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<a name="libgwyddion-GwyExpr"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle"><a name="libgwyddion-GwyExpr.top_of_page"></a>GwyExpr</span></h2>
<p>GwyExpr — Arithmetic expression parser and evaluator</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
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<div class="refsect1">
<a name="libgwyddion-GwyExpr.functions"></a><h2>Functions</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Quarks.html#GQuark"><span class="returnvalue">GQuark</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-error-quark" title="gwy_expr_error_quark ()">gwy_expr_error_quark</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="returnvalue">GwyExpr</span></a> *
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-new" title="gwy_expr_new ()">gwy_expr_new</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-free" title="gwy_expr_free ()">gwy_expr_free</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-evaluate" title="gwy_expr_evaluate ()">gwy_expr_evaluate</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-compile" title="gwy_expr_compile ()">gwy_expr_compile</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-resolve-variables" title="gwy_expr_resolve_variables ()">gwy_expr_resolve_variables</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gint"><span class="returnvalue">gint</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-get-variables" title="gwy_expr_get_variables ()">gwy_expr_get_variables</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-execute" title="gwy_expr_execute ()">gwy_expr_execute</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-vector-execute" title="gwy_expr_vector_execute ()">gwy_expr_vector_execute</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-define-constant" title="gwy_expr_define_constant ()">gwy_expr_define_constant</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-undefine-constant" title="gwy_expr_undefine_constant ()">gwy_expr_undefine_constant</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">const <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Basic-Types.html#gchar"><span class="returnvalue">gchar</span></a> *
</td>
<td class="function_name">
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-get-expression" title="gwy_expr_get_expression ()">gwy_expr_get_expression</a> <span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="libgwyddion-GwyExpr.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody>
<tr>
<td class="define_keyword">#define</td>
<td class="function_name"><a class="link" href="libgwyddion-GwyExpr.html#GWY-EXPR-ERROR:CAPS" title="GWY_EXPR_ERROR">GWY_EXPR_ERROR</a></td>
</tr>
<tr>
<td class="datatype_keyword">enum</td>
<td class="function_name"><a class="link" href="libgwyddion-GwyExpr.html#GwyExprError" title="enum GwyExprError">GwyExprError</a></td>
</tr>
<tr>
<td class="datatype_keyword"> </td>
<td class="function_name"><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr">GwyExpr</a></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="libgwyddion-GwyExpr.includes"></a><h2>Includes</h2>
<pre class="synopsis">#include <libgwyddion/gwyddion.h>
</pre>
</div>
<div class="refsect1">
<a name="libgwyddion-GwyExpr.description"></a><h2>Description</h2>
<p><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> is an expression evaluator, more precisely parser, compiler, and
evaluator. A new <a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> can be created with <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-new" title="gwy_expr_new ()"><code class="function">gwy_expr_new()</code></a>, then it can be
used to evaluate any number of expressions; when it's no longer needed, it
should be destroyed with <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-free" title="gwy_expr_free ()"><code class="function">gwy_expr_free()</code></a>.</p>
<p>Expression syntax is described in</p>
<a class="ulink" href="http://gwyddion.net/documentation/user-guide/expression-syntax.html" target="_top">Gwyddion user guide</a>.
<p>Simple arithmetic expressions without variables can be directly evaluated
with <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-evaluate" title="gwy_expr_evaluate ()"><code class="function">gwy_expr_evaluate()</code></a>.</p>
<p>Expression with variables have to be compiled first with <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-compile" title="gwy_expr_compile ()"><code class="function">gwy_expr_compile()</code></a>.
Then either <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-resolve-variables" title="gwy_expr_resolve_variables ()"><code class="function">gwy_expr_resolve_variables()</code></a> or <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-get-variables" title="gwy_expr_get_variables ()"><code class="function">gwy_expr_get_variables()</code></a> can be
used to obtain information what variables are present in the expression and
at which positions (variables are referenced by position, not name during
final evaluation because of effieiency reasons). Subsequent evaluation with
variable substitution is performed by <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-execute" title="gwy_expr_execute ()"><code class="function">gwy_expr_execute()</code></a>. It is also
possible to evaluate expression on each item of value arrays with
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-vector-execute" title="gwy_expr_vector_execute ()"><code class="function">gwy_expr_vector_execute()</code></a>.</p>
<p>One-shot evaluation of expressions without variables is easy:</p>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
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<td class="listing_code"><pre class="programlisting"><span class="usertype">GwyExpr</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">expr</span><span class="symbol">;</span>
<span class="usertype">GError</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">err </span><span class="symbol">=</span><span class="normal"> <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS">NULL</a></span><span class="symbol">;</span>
<span class="usertype">gdouble</span><span class="normal"> result</span><span class="symbol">;</span>
<span class="normal">expr </span><span class="symbol">=</span><span class="normal"> </span><span class="function"><a href="#gwy-expr-new">gwy_expr_new</a></span><span class="symbol">();</span>
<span class="keyword">if</span><span class="normal"> </span><span class="symbol">(!</span><span class="function"><a href="#gwy-expr-evaluate">gwy_expr_evaluate</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"1+2"</span><span class="symbol">,</span><span class="normal"> </span><span class="symbol">&</span><span class="normal">result</span><span class="symbol">,</span><span class="normal"> </span><span class="symbol">&</span><span class="normal">err</span><span class="symbol">))</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal"> </span><span class="comment">/* Handle compilation error */</span>
<span class="cbracket">}</span>
<span class="function"><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Warnings-and-Assertions.html#g-print">g_print</a></span><span class="symbol">(</span><span class="string">"The result: %g</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> result</span><span class="symbol">);</span>
<span class="function"><a href="#gwy-expr-free">gwy_expr_free</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">);</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p>One-shot evaluation of expressions with known variables can be performed by
defining them as constants beforehand:</p>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
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16</pre></td>
<td class="listing_code"><pre class="programlisting"><span class="usertype">GwyExpr</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">expr</span><span class="symbol">;</span>
<span class="usertype">GError</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">err </span><span class="symbol">=</span><span class="normal"> <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS">NULL</a></span><span class="symbol">;</span>
<span class="usertype">gdouble</span><span class="normal"> result</span><span class="symbol">;</span>
<span class="comment">/* Create expression and define variables as constants */</span>
<span class="normal">expr </span><span class="symbol">=</span><span class="normal"> </span><span class="function"><a href="#gwy-expr-new">gwy_expr_new</a></span><span class="symbol">();</span>
<span class="function"><a href="#gwy-expr-define-constant">gwy_expr_define_constant</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"x"</span><span class="symbol">,</span><span class="normal"> </span><span class="number">3.0</span><span class="symbol">,</span><span class="normal"> <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS">NULL</a></span><span class="symbol">);</span>
<span class="function"><a href="#gwy-expr-define-constant">gwy_expr_define_constant</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"y"</span><span class="symbol">,</span><span class="normal"> </span><span class="number">4.0</span><span class="symbol">,</span><span class="normal"> <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS">NULL</a></span><span class="symbol">);</span>
<span class="comment">/* Evaluate expression */</span>
<span class="keyword">if</span><span class="normal"> </span><span class="symbol">(!</span><span class="function"><a href="#gwy-expr-evaluate">gwy_expr_evaluate</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"hypot x,y"</span><span class="symbol">,</span><span class="normal"> </span><span class="symbol">&</span><span class="normal">result</span><span class="symbol">,</span><span class="normal"> </span><span class="symbol">&</span><span class="normal">err</span><span class="symbol">))</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal"> </span><span class="comment">/* Handle compilation error */</span>
<span class="cbracket">}</span>
<span class="function"><a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Warnings-and-Assertions.html#g-print">g_print</a></span><span class="symbol">(</span><span class="string">"The result: %g</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> result</span><span class="symbol">);</span>
<span class="function"><a href="#gwy-expr-free">gwy_expr_free</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">);</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p>When the same expression is evaluated multiple times with different
variable values and the variables are again from some known set, the
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-resolve-variables" title="gwy_expr_resolve_variables ()"><code class="function">gwy_expr_resolve_variables()</code></a> should be used (if the repeated evaluation
happens over items of some arrays, <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-vector-execute" title="gwy_expr_vector_execute ()"><code class="function">gwy_expr_vector_execute()</code></a> is more
efficient and usually simplier to use too):</p>
<div class="informalexample">
<table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
<tbody>
<tr>
<td class="listing_lines" align="right"><pre>1
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36</pre></td>
<td class="listing_code"><pre class="programlisting"><span class="usertype">GwyExpr</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">expr</span><span class="symbol">;</span>
<span class="usertype">GError</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">err </span><span class="symbol">=</span><span class="normal"> <a href="http://developer.gnome.org/doc/API/2.0/gtk/glibglib-Standard-Macros.html#NULL:CAPS">NULL</a></span><span class="symbol">;</span>
<span class="keyword">const</span><span class="normal"> <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar">gchar</a> </span><span class="symbol">*</span><span class="keyword">const</span><span class="normal"> var_names</span><span class="symbol">[]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> </span><span class="cbracket">{</span><span class="normal"> </span><span class="string">"lambda"</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"theta"</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"psi"</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"d"</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"k"</span><span class="normal"> </span><span class="cbracket">}</span><span class="symbol">;</span>
<span class="keyword">const</span><span class="normal"> </span><span class="usertype">gdouble</span><span class="normal"> var_values1</span><span class="symbol">[]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> </span><span class="cbracket">{</span><span class="normal"> </span><span class="number">300.0</span><span class="symbol">,</span><span class="normal"> </span><span class="number">0.09</span><span class="symbol">,</span><span class="normal"> </span><span class="number">2.0</span><span class="symbol">,</span><span class="normal"> </span><span class="number">52.3</span><span class="symbol">,</span><span class="normal"> </span><span class="number">1.43</span><span class="normal"> </span><span class="cbracket">}</span><span class="symbol">;</span>
<span class="keyword">const</span><span class="normal"> </span><span class="usertype">gdouble</span><span class="normal"> var_values2</span><span class="symbol">[]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> </span><span class="cbracket">{</span><span class="normal"> </span><span class="number">400.0</span><span class="symbol">,</span><span class="normal"> </span><span class="number">0.12</span><span class="symbol">,</span><span class="normal"> </span><span class="number">2.0</span><span class="symbol">,</span><span class="normal"> </span><span class="number">54.1</span><span class="symbol">,</span><span class="normal"> </span><span class="number">1.44</span><span class="normal"> </span><span class="cbracket">}</span><span class="symbol">;</span>
<span class="usertype">guint</span><span class="normal"> var_positions</span><span class="symbol">[</span><span class="function"><a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#G-N-ELEMENTS:CAPS">G_N_ELEMENTS</a></span><span class="symbol">(</span><span class="normal">var_names</span><span class="symbol">)];</span>
<span class="usertype">gdouble</span><span class="normal"> vars</span><span class="symbol">[</span><span class="function"><a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#G-N-ELEMENTS:CAPS">G_N_ELEMENTS</a></span><span class="symbol">(</span><span class="normal">var_names</span><span class="symbol">)</span><span class="normal"> </span><span class="symbol">+</span><span class="normal"> </span><span class="number">1</span><span class="symbol">];</span>
<span class="usertype">guint</span><span class="normal"> i</span><span class="symbol">;</span>
<span class="comment">/* Create expression and define constant pi */</span>
<span class="normal">expr </span><span class="symbol">=</span><span class="normal"> </span><span class="function"><a href="#gwy-expr-new">gwy_expr_new</a></span><span class="symbol">();</span>
<span class="function"><a href="#gwy-expr-define-constant">gwy_expr_define_constant</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"pi"</span><span class="symbol">,</span><span class="normal"> <a href="/usr/share/gtk-doc/html/glibglib-Numerical-Definitions.html#G-PI:CAPS">G_PI</a></span><span class="symbol">,</span><span class="normal"> <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS">NULL</a></span><span class="symbol">);</span>
<span class="comment">/* Compile expression */</span>
<span class="keyword">if</span><span class="normal"> </span><span class="symbol">(!</span><span class="function"><a href="#gwy-expr-compile">gwy_expr_compile</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> </span><span class="string">"2*pi/lambda*d*sin theta"</span><span class="symbol">,</span><span class="normal"> </span><span class="symbol">&</span><span class="normal">err</span><span class="symbol">))</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal"> </span><span class="comment">/* Handle compilation error */</span>
<span class="cbracket">}</span>
<span class="comment">/* Resolve variables */</span>
<span class="keyword">if</span><span class="normal"> </span><span class="symbol">(</span><span class="function"><a href="#gwy-expr-resolve-variables">gwy_expr_resolve_variables</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> </span><span class="function"><a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#G-N-ELEMENTS:CAPS">G_N_ELEMENTS</a></span><span class="symbol">(</span><span class="normal">var_names</span><span class="symbol">),</span>
<span class="normal"> var_names</span><span class="symbol">,</span><span class="normal"> var_positions</span><span class="symbol">))</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal"> </span><span class="comment">/* Expression contains unknown variables */</span>
<span class="cbracket">}</span>
<span class="comment">/* Evaluate first set */</span>
<span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">i </span><span class="symbol">=</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span><span class="normal"> i </span><span class="symbol"><</span><span class="normal"> </span><span class="function"><a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#G-N-ELEMENTS:CAPS">G_N_ELEMENTS</a></span><span class="symbol">(</span><span class="normal">var_names</span><span class="symbol">);</span><span class="normal"> i</span><span class="symbol">++)</span><span class="normal"> </span><span class="cbracket">{</span>
<span class="normal"> vars</span><span class="symbol">[</span><span class="normal">var_positions</span><span class="symbol">[</span><span class="normal">i</span><span class="symbol">]]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> var_values1</span><span class="symbol">[</span><span class="normal">i</span><span class="symbol">];</span>
<span class="cbracket">}</span>
<span class="function"><a href="/usr/share/gtk-doc/html/glibglib-Warnings-and-Assertions.html#g-print">g_print</a></span><span class="symbol">(</span><span class="string">"First result: %g</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> </span><span class="function"><a href="#gwy-expr-execute">gwy_expr_execute</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> vars</span><span class="symbol">));</span>
<span class="comment">/* Evaluate second set */</span>
<span class="keyword">for</span><span class="normal"> </span><span class="symbol">(</span><span class="normal">i </span><span class="symbol">=</span><span class="normal"> </span><span class="number">0</span><span class="symbol">;</span><span class="normal"> i </span><span class="symbol"><</span><span class="normal"> </span><span class="function"><a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#G-N-ELEMENTS:CAPS">G_N_ELEMENTS</a></span><span class="symbol">(</span><span class="normal">var_names</span><span class="symbol">);</span><span class="normal"> i</span><span class="symbol">++)</span>
<span class="normal"> vars</span><span class="symbol">[</span><span class="normal">var_positions</span><span class="symbol">[</span><span class="normal">i</span><span class="symbol">]]</span><span class="normal"> </span><span class="symbol">=</span><span class="normal"> var_values2</span><span class="symbol">[</span><span class="normal">i</span><span class="symbol">];</span>
<span class="function"><a href="/usr/share/gtk-doc/html/glibglib-Warnings-and-Assertions.html#g-print">g_print</a></span><span class="symbol">(</span><span class="string">"Second result: %g</span><span class="specialchar">\n</span><span class="string">"</span><span class="symbol">,</span><span class="normal"> </span><span class="function"><a href="#gwy-expr-execute">gwy_expr_execute</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">,</span><span class="normal"> vars</span><span class="symbol">));</span>
<span class="function"><a href="#gwy-expr-free">gwy_expr_free</a></span><span class="symbol">(</span><span class="normal">expr</span><span class="symbol">);</span></pre></td>
</tr>
</tbody>
</table>
</div>
<p>The most general case is when the variables are from a large set (or
completely arbitrary). Then it is best to get the list of variables with
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-get-variables" title="gwy_expr_get_variables ()"><code class="function">gwy_expr_get_variables()</code></a> and supply only values of variables that
are actually present in the expression.</p>
</div>
<div class="refsect1">
<a name="libgwyddion-GwyExpr.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="gwy-expr-error-quark"></a><h3>gwy_expr_error_quark ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Quarks.html#GQuark"><span class="returnvalue">GQuark</span></a>
gwy_expr_error_quark (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>Returns error domain for expression parsin and evaluation.</p>
<p>See and use <a class="link" href="libgwyddion-GwyExpr.html#GWY-EXPR-ERROR:CAPS" title="GWY_EXPR_ERROR"><code class="literal">GWY_EXPR_ERROR</code></a>.</p>
<div class="refsect3">
<a name="gwy-expr-error-quark.returns"></a><h4>Returns</h4>
<p> The error domain.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-new"></a><h3>gwy_expr_new ()</h3>
<pre class="programlisting"><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="returnvalue">GwyExpr</span></a> *
gwy_expr_new (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>Creates a new expression evaluator.</p>
<div class="refsect3">
<a name="gwy-expr-new.returns"></a><h4>Returns</h4>
<p> A newly created expression evaluator.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-free"></a><h3>gwy_expr_free ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
gwy_expr_free (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>);</pre>
<p>Frees all memory used by an expression evaluator.</p>
<div class="refsect3">
<a name="gwy-expr-free.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-evaluate"></a><h3>gwy_expr_evaluate ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
gwy_expr_evaluate (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code>const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *text</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *result</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Error-Reporting.html#GError"><span class="type">GError</span></a> **err</code></em>);</pre>
<p>Evaulates an arithmetic expression.</p>
<div class="refsect3">
<a name="gwy-expr-evaluate.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>text</p></td>
<td class="parameter_description"><p>String containing the expression to evaluate.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>result</p></td>
<td class="parameter_description"><p>Location to store result to.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>err</p></td>
<td class="parameter_description"><p>Location to store compilation or evaluation error to, or <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>.
Errors from <a class="link" href="libgwyddion-GwyExpr.html#GwyExprError" title="enum GwyExprError"><span class="type">GwyExprError</span></a> domain can occur.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-evaluate.returns"></a><h4>Returns</h4>
<p> <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> on success, <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> if evaluation failed.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-compile"></a><h3>gwy_expr_compile ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
gwy_expr_compile (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code>const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *text</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Error-Reporting.html#GError"><span class="type">GError</span></a> **err</code></em>);</pre>
<p>Compiles an expression for later execution.</p>
<p>This function is useful for expressions with variables. For normal
arithmetic expressions it's easier to use <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-evaluate" title="gwy_expr_evaluate ()"><code class="function">gwy_expr_evaluate()</code></a>.</p>
<div class="refsect3">
<a name="gwy-expr-compile.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>text</p></td>
<td class="parameter_description"><p>String containing the expression to compile.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>err</p></td>
<td class="parameter_description"><p>Location to store compilation or evaluation error to, or <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>.
Errors from <a class="link" href="libgwyddion-GwyExpr.html#GwyExprError" title="enum GwyExprError"><span class="type">GwyExprError</span></a> domain can occur.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-compile.returns"></a><h4>Returns</h4>
<p> <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> on success, <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> if compilation failed.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-resolve-variables"></a><h3>gwy_expr_resolve_variables ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a>
gwy_expr_resolve_variables (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#guint"><span class="type">guint</span></a> n</code></em>,
<em class="parameter"><code>const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar"><span class="type">gchar</span></a> * const *names</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#guint"><span class="type">guint</span></a> *indices</code></em>);</pre>
<p>Finds positions of variables in an expression.</p>
<div class="refsect3">
<a name="gwy-expr-resolve-variables.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n</p></td>
<td class="parameter_description"><p>The length of <em class="parameter"><code>names</code></em>
and <em class="parameter"><code>indices</code></em>
arrays.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>names</p></td>
<td class="parameter_description"><p>List of variable names to get positions of.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>indices</p></td>
<td class="parameter_description"><p>Array to store variable positions to. The positions are the same
as in <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-execute" title="gwy_expr_execute ()"><code class="function">gwy_expr_execute()</code></a>. Variables not present in the expression
are assigned (reserved) position 0. This allows to safely
substitute values of all variables before execution wthout caring
which variables are actually present.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-resolve-variables.returns"></a><h4>Returns</h4>
<p> The number of remaining, unresolved variables in <em class="parameter"><code>expr</code></em>
.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-get-variables"></a><h3>gwy_expr_get_variables ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gint"><span class="returnvalue">gint</span></a>
gwy_expr_get_variables (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar"><span class="type">gchar</span></a> ***names</code></em>);</pre>
<p>Get the number, names, and indices of unresolved identifiers in <em class="parameter"><code>expr</code></em>
.</p>
<p>It is an error to call this function after an unsuccessful compilation.</p>
<p>If you only care about variables from a prefedined set, that is if any
unknown variable is an error, it's easier to use
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-resolve-variables" title="gwy_expr_resolve_variables ()"><code class="function">gwy_expr_resolve_variables()</code></a>.</p>
<p>The position of each variable in <em class="parameter"><code>names</code></em>
corresponds to the position of its
value in <em class="parameter"><code>values</code></em>
array in <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-execute" title="gwy_expr_execute ()"><code class="function">gwy_expr_execute()</code></a> call. Namely, the first item
in the array is always reserved and do not correspond to any variable.</p>
<div class="refsect3">
<a name="gwy-expr-get-variables.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>names</p></td>
<td class="parameter_description"><p>Location to store pointer to array of variable names to (may be
<a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a> to get just number of variables). The string array returned
in this argument in owned by <em class="parameter"><code>expr</code></em>
and is valid only until next
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-compile" title="gwy_expr_compile ()"><code class="function">gwy_expr_compile()</code></a>, <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-evaluate" title="gwy_expr_evaluate ()"><code class="function">gwy_expr_evaluate()</code></a>, or <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-free" title="gwy_expr_free ()"><code class="function">gwy_expr_free()</code></a>
call.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-get-variables.returns"></a><h4>Returns</h4>
<p> The length of array stored to <em class="parameter"><code>names</code></em>
. This is the number of
variables plus one (for the first reserved item).
On failure, 0 is returned.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-execute"></a><h3>gwy_expr_execute ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="returnvalue">gdouble</span></a>
gwy_expr_execute (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code>const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *values</code></em>);</pre>
<p>Executes a compiled expression with variables, substituting given values.</p>
<div class="refsect3">
<a name="gwy-expr-execute.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>values</p></td>
<td class="parameter_description"><p>Array with variable values. Its zeroth item is always unused.
Variable list can be obtained by <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-get-variables" title="gwy_expr_get_variables ()"><code class="function">gwy_expr_get_variables()</code></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-execute.returns"></a><h4>Returns</h4>
<p> The result.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-vector-execute"></a><h3>gwy_expr_vector_execute ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
gwy_expr_vector_execute (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#guint"><span class="type">guint</span></a> n</code></em>,
<em class="parameter"><code>const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> **data</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> *result</code></em>);</pre>
<p>Executes a compiled expression on each item of data arrays.</p>
<div class="refsect3">
<a name="gwy-expr-vector-execute.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>n</p></td>
<td class="parameter_description"><p>The lenght of <em class="parameter"><code>result</code></em>
and of <em class="parameter"><code>data</code></em>
member arrays, that is vector length.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>data</p></td>
<td class="parameter_description"><p>An array of arrays of length <em class="parameter"><code>n</code></em>
. The arrays correspond to expression
variables in <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-execute" title="gwy_expr_execute ()"><code class="function">gwy_expr_execute()</code></a>. Zeroth array can be <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>result</p></td>
<td class="parameter_description"><p>An array of length <em class="parameter"><code>n</code></em>
to store computation results to. It may be
one of those in <em class="parameter"><code>data</code></em>
.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-define-constant"></a><h3>gwy_expr_define_constant ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
gwy_expr_define_constant (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code>const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *name</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gdouble"><span class="type">gdouble</span></a> value</code></em>,
<em class="parameter"><code><a href="/usr/share/gtk-doc/html/glibglib-Error-Reporting.html#GError"><span class="type">GError</span></a> **err</code></em>);</pre>
<p>Defines a symbolic constant.</p>
<p>Note the definition does not affect already compiled expression, you have
to recompile it (and eventually re-resolve variables).</p>
<div class="refsect3">
<a name="gwy-expr-define-constant.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>name</p></td>
<td class="parameter_description"><p>Name of constant to define.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>value</p></td>
<td class="parameter_description"><p>Constant numeric value.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>err</p></td>
<td class="parameter_description"><p>Location to store error to, or <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#NULL:CAPS"><code class="literal">NULL</code></a>.
Only <a class="link" href="libgwyddion-GwyExpr.html#GWY-EXPR-ERROR-CONSTANT-NAME:CAPS"><code class="literal">GWY_EXPR_ERROR_CONSTANT_NAME</code></a> error from <a class="link" href="libgwyddion-GwyExpr.html#GwyExprError" title="enum GwyExprError"><span class="type">GwyExprError</span></a> domain can
occur.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-define-constant.returns"></a><h4>Returns</h4>
<p> <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> on success, <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> if definition failed.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-undefine-constant"></a><h3>gwy_expr_undefine_constant ()</h3>
<pre class="programlisting"><a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a>
gwy_expr_undefine_constant (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>,
<em class="parameter"><code>const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar"><span class="type">gchar</span></a> *name</code></em>);</pre>
<p>Undefines a symbolic constant.</p>
<p>Note the definition removal does not affect already compiled expression,
you have to recompile it (and eventually re-resolve variables).</p>
<div class="refsect3">
<a name="gwy-expr-undefine-constant.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>name</p></td>
<td class="parameter_description"><p>Name of constant to undefine.</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-undefine-constant.returns"></a><h4>Returns</h4>
<p> <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if there was such a constant and was removed, <a href="/usr/share/gtk-doc/html/glibglib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a>
otherwise.</p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="gwy-expr-get-expression"></a><h3>gwy_expr_get_expression ()</h3>
<pre class="programlisting">const <a href="/usr/share/gtk-doc/html/glibglib-Basic-Types.html#gchar"><span class="returnvalue">gchar</span></a> *
gwy_expr_get_expression (<em class="parameter"><code><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> *expr</code></em>);</pre>
<p>Gets the expression string.</p>
<div class="refsect3">
<a name="gwy-expr-get-expression.parameters"></a><h4>Parameters</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>expr</p></td>
<td class="parameter_description"><p>An expression evaluator.</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="gwy-expr-get-expression.returns"></a><h4>Returns</h4>
<p> The last string passed to <a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-evaluate" title="gwy_expr_evaluate ()"><code class="function">gwy_expr_evaluate()</code></a> or
<a class="link" href="libgwyddion-GwyExpr.html#gwy-expr-compile" title="gwy_expr_compile ()"><code class="function">gwy_expr_compile()</code></a>. It is owned by <em class="parameter"><code>expr</code></em>
and must not be modified
or freed.</p>
</div>
</div>
</div>
<div class="refsect1">
<a name="libgwyddion-GwyExpr.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="GWY-EXPR-ERROR:CAPS"></a><h3>GWY_EXPR_ERROR</h3>
<pre class="programlisting">#define GWY_EXPR_ERROR gwy_expr_error_quark()
</pre>
<p>Error domain for expression parsing and evaluation. Errors in this domain
will be from the <a class="link" href="libgwyddion-GwyExpr.html#GwyExprError" title="enum GwyExprError"><span class="type">GwyExprError</span></a> enumeration. See <a href="/usr/share/gtk-doc/html/glibglib-Error-Reporting.html#GError"><span class="type">GError</span></a> for information on
error domains.</p>
</div>
<hr>
<div class="refsect2">
<a name="GwyExprError"></a><h3>enum GwyExprError</h3>
<p>Error codes returned by expression parsing and execution.</p>
<div class="refsect3">
<a name="GwyExprError.members"></a><h4>Members</h4>
<div class="informaltable"><table class="informaltable" width="100%" border="0">
<colgroup>
<col width="300px" class="enum_members_name">
<col class="enum_members_description">
<col width="200px" class="enum_members_annotations">
</colgroup>
<tbody>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-CLOSING-PARENTHESIS:CAPS"></a>GWY_EXPR_ERROR_CLOSING_PARENTHESIS</p></td>
<td class="enum_member_description">
<p>A closing parenthesis is missing.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-EMPTY:CAPS"></a>GWY_EXPR_ERROR_EMPTY</p></td>
<td class="enum_member_description">
<p>Expression is empty.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-EMPTY-PARENTHESES:CAPS"></a>GWY_EXPR_ERROR_EMPTY_PARENTHESES</p></td>
<td class="enum_member_description">
<p>A parentheses pair contain nothing
inside.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-GARBAGE:CAPS"></a>GWY_EXPR_ERROR_GARBAGE</p></td>
<td class="enum_member_description">
<p>An symbol unexpectedly managed to survive.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-INVALID-ARGUMENT:CAPS"></a>GWY_EXPR_ERROR_INVALID_ARGUMENT</p></td>
<td class="enum_member_description">
<p>Function or operator argument is not a
value.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-INVALID-TOKEN:CAPS"></a>GWY_EXPR_ERROR_INVALID_TOKEN</p></td>
<td class="enum_member_description">
<p>Expression contains an invalid token.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-MISSING-ARGUMENT:CAPS"></a>GWY_EXPR_ERROR_MISSING_ARGUMENT</p></td>
<td class="enum_member_description">
<p>Function or operator arguments is missing.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-NOT-EXECUTABLE:CAPS"></a>GWY_EXPR_ERROR_NOT_EXECUTABLE</p></td>
<td class="enum_member_description">
<p>Compiled stack is not executable.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-OPENING-PARENTHESIS:CAPS"></a>GWY_EXPR_ERROR_OPENING_PARENTHESIS</p></td>
<td class="enum_member_description">
<p>An opening parenthesis is missing.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-STRAY-COMMA:CAPS"></a>GWY_EXPR_ERROR_STRAY_COMMA</p></td>
<td class="enum_member_description">
<p>A comma at the start or end of list.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-UNRESOLVED-IDENTIFIERS:CAPS"></a>GWY_EXPR_ERROR_UNRESOLVED_IDENTIFIERS</p></td>
<td class="enum_member_description">
<p>Expression contains unresolved
identifiers.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
<tr>
<td class="enum_member_name"><p><a name="GWY-EXPR-ERROR-CONSTANT-NAME:CAPS"></a>GWY_EXPR_ERROR_CONSTANT_NAME</p></td>
<td class="enum_member_description">
<p>Constant name is invalid.</p>
</td>
<td class="enum_member_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="GwyExpr"></a><h3>GwyExpr</h3>
<pre class="programlisting">typedef struct _GwyExpr GwyExpr;</pre>
<p><a class="link" href="libgwyddion-GwyExpr.html#GwyExpr" title="GwyExpr"><span class="type">GwyExpr</span></a> is an opaque data structure and should be only manipulated with the
functions below.</p>
</div>
</div>
</div>
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