/usr/share/gap/lib/options.gd is in gap-libs 4r6p5-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 | #############################################################################
##
#W options.gd GAP library Steve Linton
##
##
#Y Copyright (C) 1997, Lehrstuhl D für Mathematik, RWTH Aachen, Germany
#Y (C) 1998 School Math and Comp. Sci., University of St Andrews, Scotland
#Y Copyright (C) 2002 The GAP Group
##
## <#GAPDoc Label="[1]{options}">
## &GAP; supports a <E>global options system</E>. This is intended as a
## way for the user to provide guidance to various algorithms that
## might be used in a computation. Such guidance should not change
## mathematically the specification of the computation to be
## performed, although it may change the algorithm used. A typical
## example is the selection of a strategy for the Todd-Coxeter coset
## enumeration procedure. An example of something not suited to the
## options mechanism is the imposition of exponent laws in the
## <M>p</M>-Quotient algorithm.
## <P/>
## The basis of this system is a global stack of records. All the
## entries of each record are thought of as options settings, and the
## effective setting of an option is given by the topmost record
## in which the relevant field is bound.
## <P/>
## The reason for the choice of a stack is the intended pattern of use:
## <P/>
## <C>PushOptions( rec( <A>stuff</A> ) );</C>
## <P/>
## <C>DoSomething( <A>args</A> );</C>
## <P/>
## <C>PopOptions();</C>
## <P/>
## This can be abbreviated,
## to <C>DoSomething( <A>args</A> : <A>stuff</A> );</C> with
## a small additional abbreviation of <A>stuff</A> permitted. See
## <Ref Subsect="Function Call With Options"/> for details. The full form
## can be used where the same options are to run across several
## calls, or where the <C>DoSomething</C> procedure is actually an infix
## operator, or other function with special syntax.
## <P/>
## An alternative to this system is the use of additional optional
## arguments in procedure calls. This is not felt to be sufficient
## because many procedure calls might cause, for example, a coset
## enumeration and each would need to make provision for the
## possibility of extra arguments. In this system the options are
## pushed when the user-level procedure is called, and remain in
## effect (unless altered) for all procedures called by it.
## <P/>
## Note that in some places in the system optional records containing
## options which are valid only for the immediate function or method
## call are in fact used.
## <#/GAPDoc>
##
#############################################################################
##
#F PushOptions( <options record> ) set new options
##
## <#GAPDoc Label="PushOptions">
## <ManSection>
## <Func Name="PushOptions" Arg='options record'/>
##
## <Description>
## This function pushes a record of options onto the global option stack.
## Note that <C>PushOptions( rec( <A>opt</A>:= fail ) )</C> has the effect
## of resetting the option <A>opt</A>, since an option that has never been
## set has the value <K>fail</K> returned by <Ref Func="ValueOption"/>.
## <P/>
## Note that there is no check for misspelt or undefined options.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction( "PushOptions");
#############################################################################
##
#F PopOptions( ) remove options
##
## <#GAPDoc Label="PopOptions">
## <ManSection>
## <Func Name="PopOptions" Arg=''/>
##
## <Description>
## This function removes the top-most options record from the options stack
## if there is one.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction( "PopOptions");
#############################################################################
##
#F ResetOptionsStack( ) remove all options
##
## <#GAPDoc Label="ResetOptionsStack">
## <ManSection>
## <Func Name="ResetOptionsStack" Arg=''/>
##
## <Description>
## unbinds (i.e. removes) all the options records from the options stack.
## <P/>
## <E>Note:</E>
## <Ref Func="ResetOptionsStack"/> should <E>not</E> be used within a
## function.
## Its intended use is to clean up the options stack in the event
## that the user has <K>quit</K> from a <K>break</K> loop,
## so leaving a stack of no-longer-needed options
## (see <Ref Subsect="quit"/>).
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction( "ResetOptionsStack");
#############################################################################
##
#F OnQuit( ) currently removes all options
##
## <#GAPDoc Label="OnQuit">
## <ManSection>
## <Func Name="OnQuit" Arg=''/>
##
## <Description>
## called when a user selects to <C>quit;</C> a break loop entered via
## execution of <Ref Func="Error"/>.
## As &GAP; starts up, <Ref Func="OnQuit"/> is defined to do nothing,
## in case an error is encountered during &GAP; start-up.
## Here we redefine <Ref Func="OnQuit"/> to do a variant of
## <Ref Func="ResetOptionsStack"/> to ensure the options stack is empty
## after a user quits an <Ref Func="Error"/>-induced break loop.
## (<Ref Func="OnQuit"/> differs from <Ref Func="ResetOptionsStack"/>
## in that it warns when it does something rather than the other way round.)
## Currently, <Ref Func="OnQuit"/> is not advertised,
## since exception handling may make it obsolete.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
#Unbind(OnQuit); # We don't do this because it would leave
#DeclareGlobalFunction( "OnQuit" ); # us vulnerable to an Error happening
# before OnQuit's definition is installed
#############################################################################
##
#F ValueOption( <opt> )
##
## <#GAPDoc Label="ValueOption">
## <ManSection>
## <Func Name="ValueOption" Arg='opt'/>
##
## <Description>
## This function is a method for accessing the options stack without
## changing it;
## <A>opt</A> should be the name of an option, i.e. a string.
## A function which makes decisions that might be affected by options
## should examine the result of <Ref Func="ValueOption"/>.
## If <A>opt</A> is currently not set then <K>fail</K> is returned.
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction( "ValueOption");
#############################################################################
##
#F DisplayOptionsStack( ) display the options stack
##
## <#GAPDoc Label="DisplayOptionsStack">
## <ManSection>
## <Func Name="DisplayOptionsStack" Arg=''/>
##
## <Description>
## This function prints a human-readable display of the complete
## options stack.
## <P/>
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareGlobalFunction( "DisplayOptionsStack");
#############################################################################
##
#V InfoOptions info class for options
##
## <#GAPDoc Label="InfoOptions">
## <ManSection>
## <InfoClass Name="InfoOptions"/>
##
## <Description>
## This info class can be used to enable messages about options being
## changed (level 1) or accessed (level 2).
## </Description>
## </ManSection>
## <#/GAPDoc>
##
DeclareInfoClass("InfoOptions");
#############################################################################
##
#E
|