nim 0.12.0-2 / usr / lib / nim / pure / strutils.nim

#
#
#            Nim's Runtime Library
#        (c) Copyright 2012 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## This module contains various string utility routines.
## See the module `re <re.html>`_ for regular expression support.
## See the module `pegs <pegs.html>`_ for PEG support.
## This module is available for the `JavaScript target
## <backends.html#the-javascript-target>`_.

import parseutils

{.deadCodeElim: on.}

{.push debugger:off .} # the user does not want to trace a part
                       # of the standard library!

include "system/inclrtl"

{.pop.}

type
  CharSet* {.deprecated.} = set[char] # for compatibility with Nim
{.deprecated: [TCharSet: CharSet].}

const
  Whitespace* = {' ', '\t', '\v', '\r', '\l', '\f'}
    ## All the characters that count as whitespace.

  Letters* = {'A'..'Z', 'a'..'z'}
    ## the set of letters

  Digits* = {'0'..'9'}
    ## the set of digits

  HexDigits* = {'0'..'9', 'A'..'F', 'a'..'f'}
    ## the set of hexadecimal digits

  IdentChars* = {'a'..'z', 'A'..'Z', '0'..'9', '_'}
    ## the set of characters an identifier can consist of

  IdentStartChars* = {'a'..'z', 'A'..'Z', '_'}
    ## the set of characters an identifier can start with

  NewLines* = {'\13', '\10'}
    ## the set of characters a newline terminator can start with

  AllChars* = {'\x00'..'\xFF'}
    ## A set with all the possible characters.
    ##
    ## Not very useful by its own, you can use it to create *inverted* sets to
    ## make the `find() proc <#find,string,set[char],int>`_ find **invalid**
    ## characters in strings.  Example:
    ##
    ## .. code-block:: nim
    ##   let invalid = AllChars - Digits
    ##   doAssert "01234".find(invalid) == -1
    ##   doAssert "01A34".find(invalid) == 2

proc isAlpha*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaChar".}=
  ## Checks whether or not `c` is alphabetical.
  ##
  ## This checks a-z, A-Z ASCII characters only.
  return c in Letters

proc isAlphaNumeric*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaNumericChar".}=
  ## Checks whether or not `c` is alphanumeric.
  ##
  ## This checks a-z, A-Z, 0-9 ASCII characters only.
  return c in Letters or c in Digits

proc isDigit*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsDigitChar".}=
  ## Checks whether or not `c` is a number.
  ##
  ## This checks 0-9 ASCII characters only.
  return c in Digits

proc isSpace*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsSpaceChar".}=
  ## Checks whether or not `c` is a whitespace character.
  return c in Whitespace

proc isLower*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsLowerChar".}=
  ## Checks whether or not `c` is a lower case character.
  ##
  ## This checks ASCII characters only.
  return c in {'a'..'z'}

proc isUpper*(c: char): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsUpperChar".}=
  ## Checks whether or not `c` is an upper case character.
  ##
  ## This checks ASCII characters only.
  return c in {'A'..'Z'}

proc isAlpha*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaStr".}=
  ## Checks whether or not `s` is alphabetical.
  ##
  ## This checks a-z, A-Z ASCII characters only.
  ## Returns true if all characters in `s` are
  ## alphabetic and there is at least one character
  ## in `s`.
  if s.len() == 0:
    return false

  result = true
  for c in s:
    result = c.isAlpha() and result

proc isAlphaNumeric*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsAlphaNumericStr".}=
  ## Checks whether or not `s` is alphanumeric.
  ##
  ## This checks a-z, A-Z, 0-9 ASCII characters only.
  ## Returns true if all characters in `s` are
  ## alpanumeric and there is at least one character
  ## in `s`.
  if s.len() == 0:
    return false

  result = true
  for c in s:
    result = c.isAlphaNumeric() and result

proc isDigit*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsDigitStr".}=
  ## Checks whether or not `s` is a numeric value.
  ##
  ## This checks 0-9 ASCII characters only.
  ## Returns true if all characters in `s` are
  ## numeric and there is at least one character
  ## in `s`.
  if s.len() == 0:
    return false

  result = true
  for c in s:
    result = c.isDigit() and result

proc isSpace*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsSpaceStr".}=
  ## Checks whether or not `s` is completely whitespace.
  ##
  ## Returns true if all characters in `s` are whitespace
  ## characters and there is at least one character in `s`.
  if s.len() == 0:
    return false

  result = true
  for c in s:
    result = c.isSpace() and result

proc isLower*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsLowerStr".}=
  ## Checks whether or not `s` contains all lower case characters.
  ##
  ## This checks ASCII characters only.
  ## Returns true if all characters in `s` are lower case
  ## and there is at least one character  in `s`.
  if s.len() == 0:
    return false

  result = true
  for c in s:
    result = c.isLower() and result

proc isUpper*(s: string): bool {.noSideEffect, procvar,
  rtl, extern: "nsuIsUpperStr".}=
  ## Checks whether or not `s` contains all upper case characters.
  ##
  ## This checks ASCII characters only.
  ## Returns true if all characters in `s` are upper case
  ## and there is at least one character in `s`.
  if s.len() == 0:
    return false

  result = true
  for c in s:
    result = c.isUpper() and result

proc toLower*(c: char): char {.noSideEffect, procvar,
  rtl, extern: "nsuToLowerChar".} =
  ## Converts `c` into lower case.
  ##
  ## This works only for the letters ``A-Z``. See `unicode.toLower
  ## <unicode.html#toLower>`_ for a version that works for any Unicode
  ## character.
  if c in {'A'..'Z'}:
    result = chr(ord(c) + (ord('a') - ord('A')))
  else:
    result = c

proc toLower*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuToLowerStr".} =
  ## Converts `s` into lower case.
  ##
  ## This works only for the letters ``A-Z``. See `unicode.toLower
  ## <unicode.html#toLower>`_ for a version that works for any Unicode
  ## character.
  result = newString(len(s))
  for i in 0..len(s) - 1:
    result[i] = toLower(s[i])

proc toUpper*(c: char): char {.noSideEffect, procvar,
  rtl, extern: "nsuToUpperChar".} =
  ## Converts `c` into upper case.
  ##
  ## This works only for the letters ``A-Z``.  See `unicode.toUpper
  ## <unicode.html#toUpper>`_ for a version that works for any Unicode
  ## character.
  if c in {'a'..'z'}:
    result = chr(ord(c) - (ord('a') - ord('A')))
  else:
    result = c

proc toUpper*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuToUpperStr".} =
  ## Converts `s` into upper case.
  ##
  ## This works only for the letters ``A-Z``.  See `unicode.toUpper
  ## <unicode.html#toUpper>`_ for a version that works for any Unicode
  ## character.
  result = newString(len(s))
  for i in 0..len(s) - 1:
    result[i] = toUpper(s[i])

proc capitalize*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuCapitalize".} =
  ## Converts the first character of `s` into upper case.
  ##
  ## This works only for the letters ``A-Z``.
  result = toUpper(s[0]) & substr(s, 1)

proc normalize*(s: string): string {.noSideEffect, procvar,
  rtl, extern: "nsuNormalize".} =
  ## Normalizes the string `s`.
  ##
  ## That means to convert it to lower case and remove any '_'. This is needed
  ## for Nim identifiers for example.
  result = newString(s.len)
  var j = 0
  for i in 0..len(s) - 1:
    if s[i] in {'A'..'Z'}:
      result[j] = chr(ord(s[i]) + (ord('a') - ord('A')))
      inc j
    elif s[i] != '_':
      result[j] = s[i]
      inc j
  if j != s.len: setLen(result, j)

proc cmpIgnoreCase*(a, b: string): int {.noSideEffect,
  rtl, extern: "nsuCmpIgnoreCase", procvar.} =
  ## Compares two strings in a case insensitive manner. Returns:
  ##
  ## | 0 iff a == b
  ## | < 0 iff a < b
  ## | > 0 iff a > b
  var i = 0
  var m = min(a.len, b.len)
  while i < m:
    result = ord(toLower(a[i])) - ord(toLower(b[i]))
    if result != 0: return
    inc(i)
  result = a.len - b.len

{.push checks: off, line_trace: off .} # this is a hot-spot in the compiler!
                                       # thus we compile without checks here

proc cmpIgnoreStyle*(a, b: string): int {.noSideEffect,
  rtl, extern: "nsuCmpIgnoreStyle", procvar.} =
  ## Compares two strings normalized (i.e. case and
  ## underscores do not matter). Returns:
  ##
  ## | 0 iff a == b
  ## | < 0 iff a < b
  ## | > 0 iff a > b
  var i = 0
  var j = 0
  while true:
    while a[i] == '_': inc(i)
    while b[j] == '_': inc(j) # BUGFIX: typo
    var aa = toLower(a[i])
    var bb = toLower(b[j])
    result = ord(aa) - ord(bb)
    if result != 0 or aa == '\0': break
    inc(i)
    inc(j)


proc strip*(s: string, leading = true, trailing = true,
            chars: set[char] = Whitespace): string
  {.noSideEffect, rtl, extern: "nsuStrip".} =
  ## Strips `chars` from `s` and returns the resulting string.
  ##
  ## If `leading` is true, leading `chars` are stripped.
  ## If `trailing` is true, trailing `chars` are stripped.
  var
    first = 0
    last = len(s)-1
  if leading:
    while s[first] in chars: inc(first)
  if trailing:
    while last >= 0 and s[last] in chars: dec(last)
  result = substr(s, first, last)

proc toOctal*(c: char): string {.noSideEffect, rtl, extern: "nsuToOctal".} =
  ## Converts a character `c` to its octal representation.
  ##
  ## The resulting string may not have a leading zero. Its length is always
  ## exactly 3.
  result = newString(3)
  var val = ord(c)
  for i in countdown(2, 0):
    result[i] = chr(val mod 8 + ord('0'))
    val = val div 8

iterator split*(s: string, seps: set[char] = Whitespace): string =
  ## Splits the string `s` into substrings using a group of separators.
  ##
  ## Substrings are separated by a substring containing only `seps`. Note
  ## that whole sequences of characters found in ``seps`` will be counted as
  ## a single split point and leading/trailing separators will be ignored.
  ## The following example:
  ##
  ## .. code-block:: nim
  ##   for word in split("  this is an  example  "):
  ##     writeLine(stdout, word)
  ##
  ## ...generates this output:
  ##
  ## .. code-block::
  ##   "this"
  ##   "is"
  ##   "an"
  ##   "example"
  ##
  ## And the following code:
  ##
  ## .. code-block:: nim
  ##   for word in split(";;this;is;an;;example;;;", {';'}):
  ##     writeLine(stdout, word)
  ##
  ## ...produces the same output as the first example. The code:
  ##
  ## .. code-block:: nim
  ##   let date = "2012-11-20T22:08:08.398990"
  ##   let separators = {' ', '-', ':', 'T'}
  ##   for number in split(date, separators):
  ##     writeLine(stdout, number)
  ##
  ## ...results in:
  ##
  ## .. code-block::
  ##   "2012"
  ##   "11"
  ##   "20"
  ##   "22"
  ##   "08"
  ##   "08.398990"
  ##
  var last = 0
  assert(not ('\0' in seps))
  while last < len(s):
    while s[last] in seps: inc(last)
    var first = last
    while last < len(s) and s[last] notin seps: inc(last) # BUGFIX!
    if first <= last-1:
      yield substr(s, first, last-1)

iterator split*(s: string, sep: char): string =
  ## Splits the string `s` into substrings using a single separator.
  ##
  ## Substrings are separated by the character `sep`.
  ## Unlike the version of the iterator which accepts a set of separator
  ## characters, this proc will not coalesce groups of the
  ## separator, returning a string for each found character. The code:
  ##
  ## .. code-block:: nim
  ##   for word in split(";;this;is;an;;example;;;", ';'):
  ##     writeLine(stdout, word)
  ##
  ## Results in:
  ##
  ## .. code-block::
  ##   ""
  ##   ""
  ##   "this"
  ##   "is"
  ##   "an"
  ##   ""
  ##   "example"
  ##   ""
  ##   ""
  ##   ""
  ##
  var last = 0
  assert('\0' != sep)
  if len(s) > 0:
    # `<=` is correct here for the edge cases!
    while last <= len(s):
      var first = last
      while last < len(s) and s[last] != sep: inc(last)
      yield substr(s, first, last-1)
      inc(last)

iterator split*(s: string, sep: string): string =
  ## Splits the string `s` into substrings using a string separator.
  ##
  ## Substrings are separated by the string `sep`.
  var last = 0
  if len(s) > 0:
    while last <= len(s):
      var first = last
      while last < len(s) and s.substr(last, last + <sep.len) != sep:
        inc(last)
      yield substr(s, first, last-1)
      inc(last, sep.len)

iterator splitLines*(s: string): string =
  ## Splits the string `s` into its containing lines.
  ##
  ## Every `character literal <manual.html#character-literals>`_ newline
  ## combination (CR, LF, CR-LF) is supported. The result strings contain no
  ## trailing ``\n``.
  ##
  ## Example:
  ##
  ## .. code-block:: nim
  ##   for line in splitLines("\nthis\nis\nan\n\nexample\n"):
  ##     writeLine(stdout, line)
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   ""
  ##   "this"
  ##   "is"
  ##   "an"
  ##   ""
  ##   "example"
  ##   ""
  var first = 0
  var last = 0
  while true:
    while s[last] notin {'\0', '\c', '\l'}: inc(last)
    yield substr(s, first, last-1)
    # skip newlines:
    if s[last] == '\l': inc(last)
    elif s[last] == '\c':
      inc(last)
      if s[last] == '\l': inc(last)
    else: break # was '\0'
    first = last

proc splitLines*(s: string): seq[string] {.noSideEffect,
  rtl, extern: "nsuSplitLines".} =
  ## The same as the `splitLines <#splitLines.i,string>`_ iterator, but is a
  ## proc that returns a sequence of substrings.
  accumulateResult(splitLines(s))

proc countLines*(s: string): int {.noSideEffect,
  rtl, extern: "nsuCountLines".} =
  ## Returns the number of new line separators in the string `s`.
  ##
  ## This is the same as ``len(splitLines(s))``, but much more efficient
  ## because it doesn't modify the string creating temporal objects. Every
  ## `character literal <manual.html#character-literals>`_ newline combination
  ## (CR, LF, CR-LF) is supported.
  ##
  ## Despite its name this proc might not actually return the *number of lines*
  ## in `s` because the concept of what a line is can vary. For example, a
  ## string like ``Hello world`` is a line of text, but the proc will return a
  ## value of zero because there are no newline separators.  Also, text editors
  ## usually don't count trailing newline characters in a text file as a new
  ## empty line, but this proc will.
  var i = 0
  while i < s.len:
    case s[i]
    of '\c':
      if s[i+1] == '\l': inc i
      inc result
    of '\l': inc result
    else: discard
    inc i

proc split*(s: string, seps: set[char] = Whitespace): seq[string] {.
  noSideEffect, rtl, extern: "nsuSplitCharSet".} =
  ## The same as the `split iterator <#split.i,string,set[char]>`_, but is a
  ## proc that returns a sequence of substrings.
  accumulateResult(split(s, seps))

proc split*(s: string, sep: char): seq[string] {.noSideEffect,
  rtl, extern: "nsuSplitChar".} =
  ## The same as the `split iterator <#split.i,string,char>`_, but is a proc
  ## that returns a sequence of substrings.
  accumulateResult(split(s, sep))

proc split*(s: string, sep: string): seq[string] {.noSideEffect,
  rtl, extern: "nsuSplitString".} =
  ## Splits the string `s` into substrings using a string separator.
  ##
  ## Substrings are separated by the string `sep`. This is a wrapper around the
  ## `split iterator <#split.i,string,string>`_.
  accumulateResult(split(s, sep))

proc toHex*(x: BiggestInt, len: Positive): string {.noSideEffect,
  rtl, extern: "nsuToHex".} =
  ## Converts `x` to its hexadecimal representation.
  ##
  ## The resulting string will be exactly `len` characters long. No prefix like
  ## ``0x`` is generated. `x` is treated as an unsigned value.
  const
    HexChars = "0123456789ABCDEF"
  var
    n = x
  result = newString(len)
  for j in countdown(len-1, 0):
    result[j] = HexChars[n and 0xF]
    n = n shr 4
    # handle negative overflow
    if n == 0 and x < 0: n = -1

proc intToStr*(x: int, minchars: Positive = 1): string {.noSideEffect,
  rtl, extern: "nsuIntToStr".} =
  ## Converts `x` to its decimal representation.
  ##
  ## The resulting string will be minimally `minchars` characters long. This is
  ## achieved by adding leading zeros.
  result = $abs(x)
  for i in 1 .. minchars - len(result):
    result = '0' & result
  if x < 0:
    result = '-' & result

proc parseInt*(s: string): int {.noSideEffect, procvar,
  rtl, extern: "nsuParseInt".} =
  ## Parses a decimal integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised.
  var L = parseutils.parseInt(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid integer: " & s)

proc parseBiggestInt*(s: string): BiggestInt {.noSideEffect, procvar,
  rtl, extern: "nsuParseBiggestInt".} =
  ## Parses a decimal integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised.
  var L = parseutils.parseBiggestInt(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid integer: " & s)

proc parseFloat*(s: string): float {.noSideEffect, procvar,
  rtl, extern: "nsuParseFloat".} =
  ## Parses a decimal floating point value contained in `s`. If `s` is not
  ## a valid floating point number, `ValueError` is raised. ``NAN``,
  ## ``INF``, ``-INF`` are also supported (case insensitive comparison).
  var L = parseutils.parseFloat(s, result, 0)
  if L != s.len or L == 0:
    raise newException(ValueError, "invalid float: " & s)

proc parseHexInt*(s: string): int {.noSideEffect, procvar,
  rtl, extern: "nsuParseHexInt".} =
  ## Parses a hexadecimal integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised. `s` can have one
  ## of the following optional prefixes: ``0x``, ``0X``, ``#``.  Underscores
  ## within `s` are ignored.
  var i = 0
  if s[i] == '0' and (s[i+1] == 'x' or s[i+1] == 'X'): inc(i, 2)
  elif s[i] == '#': inc(i)
  while true:
    case s[i]
    of '_': inc(i)
    of '0'..'9':
      result = result shl 4 or (ord(s[i]) - ord('0'))
      inc(i)
    of 'a'..'f':
      result = result shl 4 or (ord(s[i]) - ord('a') + 10)
      inc(i)
    of 'A'..'F':
      result = result shl 4 or (ord(s[i]) - ord('A') + 10)
      inc(i)
    of '\0': break
    else: raise newException(ValueError, "invalid integer: " & s)

proc parseBool*(s: string): bool =
  ## Parses a value into a `bool`.
  ##
  ## If ``s`` is one of the following values: ``y, yes, true, 1, on``, then
  ## returns `true`. If ``s`` is one of the following values: ``n, no, false,
  ## 0, off``, then returns `false`.  If ``s`` is something else a
  ## ``ValueError`` exception is raised.
  case normalize(s)
  of "y", "yes", "true", "1", "on": result = true
  of "n", "no", "false", "0", "off": result = false
  else: raise newException(ValueError, "cannot interpret as a bool: " & s)

proc parseEnum*[T: enum](s: string): T =
  ## Parses an enum ``T``.
  ##
  ## Raises ``ValueError`` for an invalid value in `s`. The comparison is
  ## done in a style insensitive way.
  for e in low(T)..high(T):
    if cmpIgnoreStyle(s, $e) == 0:
      return e
  raise newException(ValueError, "invalid enum value: " & s)

proc parseEnum*[T: enum](s: string, default: T): T =
  ## Parses an enum ``T``.
  ##
  ## Uses `default` for an invalid value in `s`. The comparison is done in a
  ## style insensitive way.
  for e in low(T)..high(T):
    if cmpIgnoreStyle(s, $e) == 0:
      return e
  result = default

proc repeat*(c: char, count: Natural): string {.noSideEffect,
  rtl, extern: "nsuRepeatChar".} =
  ## Returns a string of length `count` consisting only of
  ## the character `c`. You can use this proc to left align strings. Example:
  ##
  ## .. code-block:: nim
  ##   proc tabexpand(indent: int, text: string, tabsize: int = 4) =
  ##     echo '\t'.repeat(indent div tabsize), ' '.repeat(indent mod tabsize),
  ##         text
  ##
  ##   tabexpand(4, "At four")
  ##   tabexpand(5, "At five")
  ##   tabexpand(6, "At six")
  result = newString(count)
  for i in 0..count-1: result[i] = c

proc repeat*(s: string, n: Natural): string {.noSideEffect,
  rtl, extern: "nsuRepeatStr".} =
  ## Returns String `s` concatenated `n` times.  Example:
  ##
  ## .. code-block:: nim
  ##   echo "+++ STOP ".repeat(4), "+++"
  result = newStringOfCap(n * s.len)
  for i in 1..n: result.add(s)

template spaces*(n: Natural): string =  repeat(' ',n)
  ## Returns a String with `n` space characters. You can use this proc
  ## to left align strings. Example:
  ##
  ## .. code-block:: nim
  ##   let
  ##     width = 15
  ##     text1 = "Hello user!"
  ##     text2 = "This is a very long string"
  ##   echo text1 & spaces(max(0, width - text1.len)) & "|"
  ##   echo text2 & spaces(max(0, width - text2.len)) & "|"

proc repeatChar*(count: Natural, c: char = ' '): string {.deprecated.} =
  ## deprecated: use repeat() or spaces()
  repeat(c, count)

proc repeatStr*(count: Natural, s: string): string {.deprecated.} =
  ## deprecated: use repeat(string, count) or string.repeat(count)
  repeat(s, count)

proc align*(s: string, count: Natural, padding = ' '): string {.
  noSideEffect, rtl, extern: "nsuAlignString".} =
  ## Aligns a string `s` with `padding`, so that it is of length `count`.
  ##
  ## `padding` characters (by default spaces) are added before `s` resulting in
  ## right alignment. If ``s.len >= count``, no spaces are added and `s` is
  ## returned unchanged. If you need to left align a string use the `repeatChar
  ## proc <#repeatChar>`_. Example:
  ##
  ## .. code-block:: nim
  ##   assert align("abc", 4) == " abc"
  ##   assert align("a", 0) == "a"
  ##   assert align("1232", 6) == "  1232"
  ##   assert align("1232", 6, '#') == "##1232"
  if s.len < count:
    result = newString(count)
    let spaces = count - s.len
    for i in 0..spaces-1: result[i] = padding
    for i in spaces..count-1: result[i] = s[i-spaces]
  else:
    result = s

iterator tokenize*(s: string, seps: set[char] = Whitespace): tuple[
  token: string, isSep: bool] =
  ## Tokenizes the string `s` into substrings.
  ##
  ## Substrings are separated by a substring containing only `seps`.
  ## Examples:
  ##
  ## .. code-block:: nim
  ##   for word in tokenize("  this is an  example  "):
  ##     writeLine(stdout, word)
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   ("  ", true)
  ##   ("this", false)
  ##   (" ", true)
  ##   ("is", false)
  ##   (" ", true)
  ##   ("an", false)
  ##   ("  ", true)
  ##   ("example", false)
  ##   ("  ", true)
  var i = 0
  while true:
    var j = i
    var isSep = s[j] in seps
    while j < s.len and (s[j] in seps) == isSep: inc(j)
    if j > i:
      yield (substr(s, i, j-1), isSep)
    else:
      break
    i = j

proc wordWrap*(s: string, maxLineWidth = 80,
               splitLongWords = true,
               seps: set[char] = Whitespace,
               newLine = "\n"): string {.
               noSideEffect, rtl, extern: "nsuWordWrap".} =
  ## Word wraps `s`.
  result = newStringOfCap(s.len + s.len shr 6)
  var spaceLeft = maxLineWidth
  var lastSep = ""
  for word, isSep in tokenize(s, seps):
    if isSep:
      lastSep = word
      spaceLeft = spaceLeft - len(word)
      continue
    if len(word) > spaceLeft:
      if splitLongWords and len(word) > maxLineWidth:
        result.add(substr(word, 0, spaceLeft-1))
        var w = spaceLeft+1
        var wordLeft = len(word) - spaceLeft
        while wordLeft > 0:
          result.add(newLine)
          var L = min(maxLineWidth, wordLeft)
          spaceLeft = maxLineWidth - L
          result.add(substr(word, w, w+L-1))
          inc(w, L)
          dec(wordLeft, L)
      else:
        spaceLeft = maxLineWidth - len(word)
        result.add(newLine)
        result.add(word)
    else:
      spaceLeft = spaceLeft - len(word)
      result.add(lastSep & word)
      lastSep.setLen(0)

proc indent*(s: string, count: Natural, padding: string = " "): string
    {.noSideEffect, rtl, extern: "nsuIndent".} =
  ## Indents each line in ``s`` by ``count`` amount of ``padding``.
  ##
  ## **Note:** This currently does not preserve the specific new line characters
  ## used.
  result = ""
  var i = 0
  for line in s.splitLines():
    if i != 0:
      result.add("\n")
    for j in 1..count:
      result.add(padding)
    result.add(line)
    i.inc

proc unindent*(s: string, eatAllIndent = false): string {.
               noSideEffect, rtl, extern: "nsuUnindent".} =
  ## Unindents `s`.
  result = newStringOfCap(s.len)
  var i = 0
  var pattern = true
  var indent = 0
  while s[i] == ' ': inc i
  var level = if i == 0: -1 else: i
  while i < s.len:
    if s[i] == ' ':
      if i > 0 and s[i-1] in {'\l', '\c'}:
        pattern = true
        indent = 0
      if pattern:
        inc(indent)
        if indent > level and not eatAllIndent:
          result.add(s[i])
        if level < 0: level = indent
      else:
        # a space somewhere: do not delete
        result.add(s[i])
    else:
      pattern = false
      result.add(s[i])
    inc i

proc startsWith*(s, prefix: string): bool {.noSideEffect,
  rtl, extern: "nsuStartsWith".} =
  ## Returns true iff ``s`` starts with ``prefix``.
  ##
  ## If ``prefix == ""`` true is returned.
  var i = 0
  while true:
    if prefix[i] == '\0': return true
    if s[i] != prefix[i]: return false
    inc(i)

proc endsWith*(s, suffix: string): bool {.noSideEffect,
  rtl, extern: "nsuEndsWith".} =
  ## Returns true iff ``s`` ends with ``suffix``.
  ##
  ## If ``suffix == ""`` true is returned.
  var i = 0
  var j = len(s) - len(suffix)
  while i+j <% s.len:
    if s[i+j] != suffix[i]: return false
    inc(i)
  if suffix[i] == '\0': return true

proc continuesWith*(s, substr: string, start: Natural): bool {.noSideEffect,
  rtl, extern: "nsuContinuesWith".} =
  ## Returns true iff ``s`` continues with ``substr`` at position ``start``.
  ##
  ## If ``substr == ""`` true is returned.
  var i = 0
  while true:
    if substr[i] == '\0': return true
    if s[i+start] != substr[i]: return false
    inc(i)

proc addSep*(dest: var string, sep = ", ", startLen: Natural = 0)
  {.noSideEffect, inline.} =
  ## Adds a separator to `dest` only if its length is bigger than `startLen`.
  ##
  ## A shorthand for:
  ##
  ## .. code-block:: nim
  ##   if dest.len > startLen: add(dest, sep)
  ##
  ## This is often useful for generating some code where the items need to
  ## be *separated* by `sep`. `sep` is only added if `dest` is longer than
  ## `startLen`. The following example creates a string describing
  ## an array of integers:
  ##
  ## .. code-block:: nim
  ##   var arr = "["
  ##   for x in items([2, 3, 5, 7, 11]):
  ##     addSep(arr, startLen=len("["))
  ##     add(arr, $x)
  ##   add(arr, "]")
  if dest.len > startLen: add(dest, sep)

proc allCharsInSet*(s: string, theSet: set[char]): bool =
  ## Returns true iff each character of `s` is in the set `theSet`.
  for c in items(s):
    if c notin theSet: return false
  return true

proc abbrev*(s: string, possibilities: openArray[string]): int =
  ## Returns the index of the first item in `possibilities` if not ambiguous.
  ##
  ## Returns -1 if no item has been found and -2 if multiple items match.
  result = -1 # none found
  for i in 0..possibilities.len-1:
    if possibilities[i].startsWith(s):
      if possibilities[i] == s:
        # special case: exact match shouldn't be ambiguous
        return i
      if result >= 0: return -2 # ambiguous
      result = i

# ---------------------------------------------------------------------------

proc join*(a: openArray[string], sep: string): string {.
  noSideEffect, rtl, extern: "nsuJoinSep".} =
  ## Concatenates all strings in `a` separating them with `sep`.
  if len(a) > 0:
    var L = sep.len * (a.len-1)
    for i in 0..high(a): inc(L, a[i].len)
    result = newStringOfCap(L)
    add(result, a[0])
    for i in 1..high(a):
      add(result, sep)
      add(result, a[i])
  else:
    result = ""

proc join*(a: openArray[string]): string {.
  noSideEffect, rtl, extern: "nsuJoin".} =
  ## Concatenates all strings in `a`.
  if len(a) > 0:
    var L = 0
    for i in 0..high(a): inc(L, a[i].len)
    result = newStringOfCap(L)
    for i in 0..high(a): add(result, a[i])
  else:
    result = ""

type
  SkipTable = array[char, int]

proc preprocessSub(sub: string, a: var SkipTable) =
  var m = len(sub)
  for i in 0..0xff: a[chr(i)] = m+1
  for i in 0..m-1: a[sub[i]] = m-i

proc findAux(s, sub: string, start: int, a: SkipTable): int =
  # Fast "quick search" algorithm:
  var
    m = len(sub)
    n = len(s)
  # search:
  var j = start
  while j <= n - m:
    block match:
      for k in 0..m-1:
        if sub[k] != s[k+j]: break match
      return j
    inc(j, a[s[j+m]])
  return -1

proc find*(s, sub: string, start: Natural = 0): int {.noSideEffect,
  rtl, extern: "nsuFindStr".} =
  ## Searches for `sub` in `s` starting at position `start`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  var a {.noinit.}: SkipTable
  preprocessSub(sub, a)
  result = findAux(s, sub, start, a)

proc find*(s: string, sub: char, start: Natural = 0): int {.noSideEffect,
  rtl, extern: "nsuFindChar".} =
  ## Searches for `sub` in `s` starting at position `start`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  for i in start..len(s)-1:
    if sub == s[i]: return i
  return -1

proc find*(s: string, chars: set[char], start: Natural = 0): int {.noSideEffect,
  rtl, extern: "nsuFindCharSet".} =
  ## Searches for `chars` in `s` starting at position `start`.
  ##
  ## If `s` contains none of the characters in `chars`, -1 is returned.
  for i in start..s.len-1:
    if s[i] in chars: return i
  return -1

proc rfind*(s, sub: string, start: int = -1): int {.noSideEffect.} =
  ## Searches for `sub` in `s` in reverse, starting at `start` and going
  ## backwards to 0.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  let realStart = if start == -1: s.len else: start
  for i in countdown(realStart-sub.len, 0):
    for j in 0..sub.len-1:
      result = i
      if sub[j] != s[i+j]:
        result = -1
        break
    if result != -1: return
  return -1

proc rfind*(s: string, sub: char, start: int = -1): int {.noSideEffect,
  rtl.} =
  ## Searches for `sub` in `s` in reverse starting at position `start`.
  ##
  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
  let realStart = if start == -1: s.len-1 else: start
  for i in countdown(realStart, 0):
    if sub == s[i]: return i
  return -1

proc count*(s: string, sub: string, overlapping: bool = false): int {.
  noSideEffect, rtl, extern: "nsuCountString".} =
  ## Count the occurrences of a substring `sub` in the string `s`.
  ## Overlapping occurrences of `sub` only count when `overlapping`
  ## is set to true.
  var i = 0
  while true:
    i = s.find(sub, i)
    if i < 0:
      break
    if overlapping:
      inc i
    else:
      i += sub.len
    inc result

proc count*(s: string, sub: char): int {.noSideEffect,
  rtl, extern: "nsuCountChar".} =
  ## Count the occurrences of the character `sub` in the string `s`.
  for c in s:
    if c == sub:
      inc result

proc count*(s: string, subs: set[char]): int {.noSideEffect,
  rtl, extern: "nsuCountCharSet".} =
  ## Count the occurrences of the group of character `subs` in the string `s`.
  for c in s:
    if c in subs:
      inc result

proc quoteIfContainsWhite*(s: string): string {.deprecated.} =
  ## Returns ``'"' & s & '"'`` if `s` contains a space and does not
  ## start with a quote, else returns `s`.
  ##
  ## **DEPRECATED** as it was confused for shell quoting function.  For this
  ## application use `osproc.quoteShell <osproc.html#quoteShell>`_.
  if find(s, {' ', '\t'}) >= 0 and s[0] != '"':
    result = '"' & s & '"'
  else:
    result = s

proc contains*(s: string, c: char): bool {.noSideEffect.} =
  ## Same as ``find(s, c) >= 0``.
  return find(s, c) >= 0

proc contains*(s, sub: string): bool {.noSideEffect.} =
  ## Same as ``find(s, sub) >= 0``.
  return find(s, sub) >= 0

proc contains*(s: string, chars: set[char]): bool {.noSideEffect.} =
  ## Same as ``find(s, chars) >= 0``.
  return find(s, chars) >= 0

proc replace*(s, sub: string, by = ""): string {.noSideEffect,
  rtl, extern: "nsuReplaceStr".} =
  ## Replaces `sub` in `s` by the string `by`.
  var a {.noinit.}: SkipTable
  result = ""
  preprocessSub(sub, a)
  var i = 0
  while true:
    var j = findAux(s, sub, i, a)
    if j < 0: break
    add result, substr(s, i, j - 1)
    add result, by
    i = j + len(sub)
  # copy the rest:
  add result, substr(s, i)

proc replace*(s: string, sub, by: char): string {.noSideEffect,
  rtl, extern: "nsuReplaceChar".} =
  ## Replaces `sub` in `s` by the character `by`.
  ##
  ## Optimized version of `replace <#replace,string,string>`_ for characters.
  result = newString(s.len)
  var i = 0
  while i < s.len:
    if s[i] == sub: result[i] = by
    else: result[i] = s[i]
    inc(i)

proc replaceWord*(s, sub: string, by = ""): string {.noSideEffect,
  rtl, extern: "nsuReplaceWord".} =
  ## Replaces `sub` in `s` by the string `by`.
  ##
  ## Each occurrence of `sub` has to be surrounded by word boundaries
  ## (comparable to ``\\w`` in regular expressions), otherwise it is not
  ## replaced.
  const wordChars = {'a'..'z', 'A'..'Z', '0'..'9', '_', '\128'..'\255'}
  var a {.noinit.}: SkipTable
  result = ""
  preprocessSub(sub, a)
  var i = 0
  while true:
    var j = findAux(s, sub, i, a)
    if j < 0: break
    # word boundary?
    if (j == 0 or s[j-1] notin wordChars) and
        (j+sub.len >= s.len or s[j+sub.len] notin wordChars):
      add result, substr(s, i, j - 1)
      add result, by
      i = j + len(sub)
    else:
      add result, substr(s, i, j)
      i = j + 1
  # copy the rest:
  add result, substr(s, i)

proc delete*(s: var string, first, last: int) {.noSideEffect,
  rtl, extern: "nsuDelete".} =
  ## Deletes in `s` the characters at position `first` .. `last`.
  ##
  ## This modifies `s` itself, it does not return a copy.
  var i = first
  var j = last+1
  var newLen = len(s)-j+i
  while i < newLen:
    s[i] = s[j]
    inc(i)
    inc(j)
  setLen(s, newLen)

proc parseOctInt*(s: string): int {.noSideEffect,
  rtl, extern: "nsuParseOctInt".} =
  ## Parses an octal integer value contained in `s`.
  ##
  ## If `s` is not a valid integer, `ValueError` is raised. `s` can have one
  ## of the following optional prefixes: ``0o``, ``0O``.  Underscores within
  ## `s` are ignored.
  var i = 0
  if s[i] == '0' and (s[i+1] == 'o' or s[i+1] == 'O'): inc(i, 2)
  while true:
    case s[i]
    of '_': inc(i)
    of '0'..'7':
      result = result shl 3 or (ord(s[i]) - ord('0'))
      inc(i)
    of '\0': break
    else: raise newException(ValueError, "invalid integer: " & s)

proc toOct*(x: BiggestInt, len: Positive): string {.noSideEffect,
  rtl, extern: "nsuToOct".} =
  ## Converts `x` into its octal representation.
  ##
  ## The resulting string is always `len` characters long. No leading ``0o``
  ## prefix is generated.
  var
    mask: BiggestInt = 7
    shift: BiggestInt = 0
  assert(len > 0)
  result = newString(len)
  for j in countdown(len-1, 0):
    result[j] = chr(int((x and mask) shr shift) + ord('0'))
    shift = shift + 3
    mask = mask shl 3

proc toBin*(x: BiggestInt, len: Positive): string {.noSideEffect,
  rtl, extern: "nsuToBin".} =
  ## Converts `x` into its binary representation.
  ##
  ## The resulting string is always `len` characters long. No leading ``0b``
  ## prefix is generated.
  var
    mask: BiggestInt = 1
    shift: BiggestInt = 0
  assert(len > 0)
  result = newString(len)
  for j in countdown(len-1, 0):
    result[j] = chr(int((x and mask) shr shift) + ord('0'))
    shift = shift + 1
    mask = mask shl 1

proc insertSep*(s: string, sep = '_', digits = 3): string {.noSideEffect,
  rtl, extern: "nsuInsertSep".} =
  ## Inserts the separator `sep` after `digits` digits from right to left.
  ##
  ## Even though the algorithm works with any string `s`, it is only useful
  ## if `s` contains a number.
  ## Example: ``insertSep("1000000") == "1_000_000"``
  var L = (s.len-1) div digits + s.len
  result = newString(L)
  var j = 0
  dec(L)
  for i in countdown(len(s)-1, 0):
    if j == digits:
      result[L] = sep
      dec(L)
      j = 0
    result[L] = s[i]
    inc(j)
    dec(L)

proc escape*(s: string, prefix = "\"", suffix = "\""): string {.noSideEffect,
  rtl, extern: "nsuEscape".} =
  ## Escapes a string `s`.
  ##
  ## This does these operations (at the same time):
  ## * replaces any ``\`` by ``\\``
  ## * replaces any ``'`` by ``\'``
  ## * replaces any ``"`` by ``\"``
  ## * replaces any other character in the set ``{'\0'..'\31', '\128'..'\255'}``
  ##   by ``\xHH`` where ``HH`` is its hexadecimal value.
  ## The procedure has been designed so that its output is usable for many
  ## different common syntaxes. The resulting string is prefixed with
  ## `prefix` and suffixed with `suffix`. Both may be empty strings.
  result = newStringOfCap(s.len + s.len shr 2)
  result.add(prefix)
  for c in items(s):
    case c
    of '\0'..'\31', '\128'..'\255':
      add(result, "\\x")
      add(result, toHex(ord(c), 2))
    of '\\': add(result, "\\\\")
    of '\'': add(result, "\\'")
    of '\"': add(result, "\\\"")
    else: add(result, c)
  add(result, suffix)

proc unescape*(s: string, prefix = "\"", suffix = "\""): string {.noSideEffect,
  rtl, extern: "nsuUnescape".} =
  ## Unescapes a string `s`.
  ##
  ## This complements `escape <#escape>`_ as it performs the opposite
  ## operations.
  ##
  ## If `s` does not begin with ``prefix`` and end with ``suffix`` a
  ## ValueError exception will be raised.
  result = newStringOfCap(s.len)
  var i = 0
  if not s.startsWith(prefix):
    raise newException(ValueError,
                       "String does not start with a prefix of: " & prefix)
  inc(i)
  while true:
    if i == s.len-suffix.len: break
    case s[i]
    of '\\':
      case s[i+1]:
      of 'x':
        inc i
        var c: int
        i += parseutils.parseHex(s, c, i)
        result.add(chr(c))
        inc(i, 2)
      of '\\':
        result.add('\\')
      of '\'':
        result.add('\'')
      of '\"':
        result.add('\"')
      else: result.add("\\" & s[i+1])
      inc(i)
    of '\0': break
    else:
      result.add(s[i])
    inc(i)
  if not s.endsWith(suffix):
    raise newException(ValueError,
                       "String does not end with a suffix of: " & suffix)

proc validIdentifier*(s: string): bool {.noSideEffect,
  rtl, extern: "nsuValidIdentifier".} =
  ## Returns true if `s` is a valid identifier.
  ##
  ## A valid identifier starts with a character of the set `IdentStartChars`
  ## and is followed by any number of characters of the set `IdentChars`.
  if s[0] in IdentStartChars:
    for i in 1..s.len-1:
      if s[i] notin IdentChars: return false
    return true

proc editDistance*(a, b: string): int {.noSideEffect,
  rtl, extern: "nsuEditDistance".} =
  ## Returns the edit distance between `a` and `b`.
  ##
  ## This uses the `Levenshtein`:idx: distance algorithm with only a linear
  ## memory overhead.  This implementation is highly optimized!
  var len1 = a.len
  var len2 = b.len
  if len1 > len2:
    # make `b` the longer string
    return editDistance(b, a)

  # strip common prefix:
  var s = 0
  while a[s] == b[s] and a[s] != '\0':
    inc(s)
    dec(len1)
    dec(len2)
  # strip common suffix:
  while len1 > 0 and len2 > 0 and a[s+len1-1] == b[s+len2-1]:
    dec(len1)
    dec(len2)
  # trivial cases:
  if len1 == 0: return len2
  if len2 == 0: return len1

  # another special case:
  if len1 == 1:
    for j in s..len2-1:
      if a[s] == b[j]: return len2 - 1
    return len2

  inc(len1)
  inc(len2)
  var half = len1 shr 1
  # initalize first row:
  #var row = cast[ptr array[0..high(int) div 8, int]](alloc(len2*sizeof(int)))
  var row: seq[int]
  newSeq(row, len2)
  var e = s + len2 - 1 # end marker
  for i in 1..len2 - half - 1: row[i] = i
  row[0] = len1 - half - 1
  for i in 1 .. len1 - 1:
    var char1 = a[i + s - 1]
    var char2p: int
    var D, x: int
    var p: int
    if i >= len1 - half:
      # skip the upper triangle:
      var offset = i - len1 + half
      char2p = offset
      p = offset
      var c3 = row[p] + ord(char1 != b[s + char2p])
      inc(p)
      inc(char2p)
      x = row[p] + 1
      D = x
      if x > c3: x = c3
      row[p] = x
      inc(p)
    else:
      p = 1
      char2p = 0
      D = i
      x = i
    if i <= half + 1:
      # skip the lower triangle:
      e = len2 + i - half - 2
    # main:
    while p <= e:
      dec(D)
      var c3 = D + ord(char1 != b[char2p + s])
      inc(char2p)
      inc(x)
      if x > c3: x = c3
      D = row[p] + 1
      if x > D: x = D
      row[p] = x
      inc(p)
    # lower triangle sentinel:
    if i <= half:
      dec(D)
      var c3 = D + ord(char1 != b[char2p + s])
      inc(x)
      if x > c3: x = c3
      row[p] = x
  result = row[e]
  #dealloc(row)


# floating point formating:

proc c_sprintf(buf, frmt: cstring): cint {.header: "<stdio.h>",
                                     importc: "sprintf", varargs, noSideEffect.}

type
  FloatFormatMode* = enum ## the different modes of floating point formating
    ffDefault,         ## use the shorter floating point notation
    ffDecimal,         ## use decimal floating point notation
    ffScientific       ## use scientific notation (using ``e`` character)

{.deprecated: [TFloatFormat: FloatFormatMode].}

proc formatBiggestFloat*(f: BiggestFloat, format: FloatFormatMode = ffDefault,
                         precision: range[0..32] = 16;
                         decimalSep = '.'): string {.
                         noSideEffect, rtl, extern: "nsu$1".} =
  ## Converts a floating point value `f` to a string.
  ##
  ## If ``format == ffDecimal`` then precision is the number of digits to
  ## be printed after the decimal point.
  ## If ``format == ffScientific`` then precision is the maximum number
  ## of significant digits to be printed.
  ## `precision`'s default value is the maximum number of meaningful digits
  ## after the decimal point for Nim's ``biggestFloat`` type.
  ##
  ## If ``precision == 0``, it tries to format it nicely.
  const floatFormatToChar: array[FloatFormatMode, char] = ['g', 'f', 'e']
  var
    frmtstr {.noinit.}: array[0..5, char]
    buf {.noinit.}: array[0..2500, char]
    L: cint
  frmtstr[0] = '%'
  if precision > 0:
    frmtstr[1] = '#'
    frmtstr[2] = '.'
    frmtstr[3] = '*'
    frmtstr[4] = floatFormatToChar[format]
    frmtstr[5] = '\0'
    L = c_sprintf(buf, frmtstr, precision, f)
  else:
    frmtstr[1] = floatFormatToChar[format]
    frmtstr[2] = '\0'
    L = c_sprintf(buf, frmtstr, f)
  result = newString(L)
  for i in 0 ..< L:
    # Depending on the locale either dot or comma is produced,
    # but nothing else is possible:
    if buf[i] in {'.', ','}: result[i] = decimalsep
    else: result[i] = buf[i]

proc formatFloat*(f: float, format: FloatFormatMode = ffDefault,
                  precision: range[0..32] = 16; decimalSep = '.'): string {.
                  noSideEffect, rtl, extern: "nsu$1".} =
  ## Converts a floating point value `f` to a string.
  ##
  ## If ``format == ffDecimal`` then precision is the number of digits to
  ## be printed after the decimal point.
  ## If ``format == ffScientific`` then precision is the maximum number
  ## of significant digits to be printed.
  ## `precision`'s default value is the maximum number of meaningful digits
  ## after the decimal point for Nim's ``float`` type.
  result = formatBiggestFloat(f, format, precision, decimalSep)

proc formatSize*(bytes: BiggestInt, decimalSep = '.'): string =
  ## Rounds and formats `bytes`. Examples:
  ##
  ## .. code-block:: nim
  ##
  ##    formatSize(1'i64 shl 31 + 300'i64) == "2.204GB"
  ##    formatSize(4096) == "4KB"
  ##
  template frmt(a, b, c: expr): expr =
    let bs = $b
    insertSep($a) & decimalSep & bs.substr(0, 2) & c
  let gigabytes = bytes shr 30
  let megabytes = bytes shr 20
  let kilobytes = bytes shr 10
  if gigabytes != 0:
    result = frmt(gigabytes, megabytes, "GB")
  elif megabytes != 0:
    result = frmt(megabytes, kilobytes, "MB")
  elif kilobytes != 0:
    result = frmt(kilobytes, bytes, "KB")
  else:
    result = insertSep($bytes) & "B"

proc findNormalized(x: string, inArray: openArray[string]): int =
  var i = 0
  while i < high(inArray):
    if cmpIgnoreStyle(x, inArray[i]) == 0: return i
    inc(i, 2) # incrementing by 1 would probably lead to a
              # security hole...
  return -1

proc invalidFormatString() {.noinline.} =
  raise newException(ValueError, "invalid format string")

proc addf*(s: var string, formatstr: string, a: varargs[string, `$`]) {.
  noSideEffect, rtl, extern: "nsuAddf".} =
  ## The same as ``add(s, formatstr % a)``, but more efficient.
  const PatternChars = {'a'..'z', 'A'..'Z', '0'..'9', '\128'..'\255', '_'}
  var i = 0
  var num = 0
  while i < len(formatstr):
    if formatstr[i] == '$':
      case formatstr[i+1] # again we use the fact that strings
                          # are zero-terminated here
      of '#':
        if num >% a.high: invalidFormatString()
        add s, a[num]
        inc i, 2
        inc num
      of '$':
        add s, '$'
        inc(i, 2)
      of '1'..'9', '-':
        var j = 0
        inc(i) # skip $
        var negative = formatstr[i] == '-'
        if negative: inc i
        while formatstr[i] in Digits:
          j = j * 10 + ord(formatstr[i]) - ord('0')
          inc(i)
        let idx = if not negative: j-1 else: a.len-j
        if idx >% a.high: invalidFormatString()
        add s, a[idx]
      of '{':
        var j = i+1
        while formatstr[j] notin {'\0', '}'}: inc(j)
        var x = findNormalized(substr(formatstr, i+2, j-1), a)
        if x >= 0 and x < high(a): add s, a[x+1]
        else: invalidFormatString()
        i = j+1
      of 'a'..'z', 'A'..'Z', '\128'..'\255', '_':
        var j = i+1
        while formatstr[j] in PatternChars: inc(j)
        var x = findNormalized(substr(formatstr, i+1, j-1), a)
        if x >= 0 and x < high(a): add s, a[x+1]
        else: invalidFormatString()
        i = j
      else:
        invalidFormatString()
    else:
      add s, formatstr[i]
      inc(i)

proc `%` *(formatstr: string, a: openArray[string]): string {.noSideEffect,
  rtl, extern: "nsuFormatOpenArray".} =
  ## Interpolates a format string with the values from `a`.
  ##
  ## The `substitution`:idx: operator performs string substitutions in
  ## `formatstr` and returns a modified `formatstr`. This is often called
  ## `string interpolation`:idx:.
  ##
  ## This is best explained by an example:
  ##
  ## .. code-block:: nim
  ##   "$1 eats $2." % ["The cat", "fish"]
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   "The cat eats fish."
  ##
  ## The substitution variables (the thing after the ``$``) are enumerated
  ## from 1 to ``a.len``.
  ## To produce a verbatim ``$``, use ``$$``.
  ## The notation ``$#`` can be used to refer to the next substitution
  ## variable:
  ##
  ## .. code-block:: nim
  ##   "$# eats $#." % ["The cat", "fish"]
  ##
  ## Substitution variables can also be words (that is
  ## ``[A-Za-z_]+[A-Za-z0-9_]*``) in which case the arguments in `a` with even
  ## indices are keys and with odd indices are the corresponding values.
  ## An example:
  ##
  ## .. code-block:: nim
  ##   "$animal eats $food." % ["animal", "The cat", "food", "fish"]
  ##
  ## Results in:
  ##
  ## .. code-block:: nim
  ##   "The cat eats fish."
  ##
  ## The variables are compared with `cmpIgnoreStyle`. `ValueError` is
  ## raised if an ill-formed format string has been passed to the `%` operator.
  result = newStringOfCap(formatstr.len + a.len shl 4)
  addf(result, formatstr, a)

proc `%` *(formatstr, a: string): string {.noSideEffect,
  rtl, extern: "nsuFormatSingleElem".} =
  ## This is the same as ``formatstr % [a]``.
  result = newStringOfCap(formatstr.len + a.len)
  addf(result, formatstr, [a])

proc format*(formatstr: string, a: varargs[string, `$`]): string {.noSideEffect,
  rtl, extern: "nsuFormatVarargs".} =
  ## This is the same as ``formatstr % a`` except that it supports
  ## auto stringification.
  result = newStringOfCap(formatstr.len + a.len)
  addf(result, formatstr, a)

{.pop.}

proc removeSuffix*(s: var string, chars: set[char] = Newlines) {.
  rtl, extern: "nsuRemoveSuffixCharSet".} =
  ## Removes the first matching character from the string (in-place) given a
  ## set of characters. If the set of characters is only equal to `Newlines`
  ## then it will remove both the newline and return feed.
  ## .. code-block:: nim
  ##   var
  ##     userInput = "Hello World!\r\n"
  ##     otherInput = "Hello!?!"
  ##   userInput.removeSuffix
  ##   userInput == "Hello World!"
  ##   userInput.removeSuffix({'!', '?'})
  ##   userInput == "Hello World"
  ##   otherInput.removeSuffix({'!', '?'})
  ##   otherInput == "Hello!?"

  var last = len(s) - 1

  if chars == Newlines:
    if s[last] == '\10':
      last -= 1

    if s[last] == '\13':
      last -= 1

  else:
    if s[last] in chars:
      last -= 1

  s.setLen(last + 1)

proc removeSuffix*(s: var string, c: char) {.
  rtl, extern: "nsuRemoveSuffixChar".} =
  ## Removes a single character (in-place) from a string.
  ## .. code-block:: nim
  ##   var
  ##     table = "users"
  ##   table.removeSuffix('s')
  ##   table == "user"
  removeSuffix(s, chars = {c})

proc removeSuffix*(s: var string, suffix: string) {.
  rtl, extern: "nsuRemoveSuffixString".} =
  ## Remove the first matching suffix (in-place) from a string.
  ## .. code-block:: nim
  ##   var
  ##     answers = "yeses"
  ##   answers.removeSuffix("es")
  ##   answers == "yes"

  var newLen = s.len

  if s.endsWith(suffix):
    newLen -= len(suffix)

  s.setLen(newLen)

when isMainModule:
  doAssert align("abc", 4) == " abc"
  doAssert align("a", 0) == "a"
  doAssert align("1232", 6) == "  1232"
  doAssert align("1232", 6, '#') == "##1232"

  let
    inp = """ this is a long text --  muchlongerthan10chars and here
               it goes"""
    outp = " this is a\nlong text\n--\nmuchlongerthan10chars\nand here\nit goes"
  doAssert wordWrap(inp, 10, false) == outp

  doAssert formatBiggestFloat(0.00000000001, ffDecimal, 11) == "0.00000000001"
  doAssert formatBiggestFloat(0.00000000001, ffScientific, 1, ',') in
                                                   ["1,0e-11", "1,0e-011"]

  doAssert "$# $3 $# $#" % ["a", "b", "c"] == "a c b c"
  when not defined(testing):
    echo formatSize(1'i64 shl 31 + 300'i64) # == "4,GB"
    echo formatSize(1'i64 shl 31)

  doAssert "$animal eats $food." % ["animal", "The cat", "food", "fish"] ==
           "The cat eats fish."

  doAssert "-ld a-ldz -ld".replaceWord("-ld") == " a-ldz "
  doAssert "-lda-ldz -ld abc".replaceWord("-ld") == "-lda-ldz  abc"

  type MyEnum = enum enA, enB, enC, enuD, enE
  doAssert parseEnum[MyEnum]("enu_D") == enuD

  doAssert parseEnum("invalid enum value", enC) == enC

  doAssert count("foofoofoo", "foofoo") == 1
  doAssert count("foofoofoo", "foofoo", overlapping = true) == 2
  doAssert count("foofoofoo", 'f') == 3
  doAssert count("foofoofoobar", {'f','b'}) == 4

  doAssert strip("  foofoofoo  ") == "foofoofoo"
  doAssert strip("sfoofoofoos", chars = {'s'}) == "foofoofoo"
  doAssert strip("barfoofoofoobar", chars = {'b', 'a', 'r'}) == "foofoofoo"
  doAssert strip("stripme but don't strip this stripme",
                 chars = {'s', 't', 'r', 'i', 'p', 'm', 'e'}) ==
                 " but don't strip this "
  doAssert strip("sfoofoofoos", leading = false, chars = {'s'}) == "sfoofoofoo"
  doAssert strip("sfoofoofoos", trailing = false, chars = {'s'}) == "foofoofoos"

  doAssert "  foo\n  bar".indent(4, "Q") == "QQQQ  foo\nQQQQ  bar"

  doAssert isAlpha('r')
  doAssert isAlpha('A')
  doAssert(not isAlpha('$'))

  doAssert isAlpha("Rasp")
  doAssert isAlpha("Args")
  doAssert(not isAlpha("$Tomato"))

  doAssert isAlphaNumeric('3')
  doAssert isAlphaNumeric('R')
  doAssert(not isAlphaNumeric('!'))

  doAssert isAlphaNumeric("34ABc")
  doAssert isAlphaNumeric("Rad")
  doAssert isAlphaNumeric("1234")
  doAssert(not isAlphaNumeric("@nose"))

  doAssert isDigit('3')
  doAssert(not isDigit('a'))
  doAssert(not isDigit('%'))

  doAssert isDigit("12533")
  doAssert(not isDigit("12.33"))
  doAssert(not isDigit("A45b"))

  doAssert isSpace('\t')
  doAssert isSpace('\l')
  doAssert(not isSpace('A'))

  doAssert isSpace("\t\l \v\r\f")
  doAssert isSpace("       ")
  doAssert(not isSpace("ABc   \td"))

  doAssert isLower('a')
  doAssert isLower('z')
  doAssert(not isLower('A'))
  doAssert(not isLower('5'))
  doAssert(not isLower('&'))

  doAssert isLower("abcd")
  doAssert(not isLower("abCD"))
  doAssert(not isLower("33aa"))

  doAssert isUpper('A')
  doAssert(not isUpper('b'))
  doAssert(not isUpper('5'))
  doAssert(not isUpper('%'))

  doAssert isUpper("ABC")
  doAssert(not isUpper("AAcc"))
  doAssert(not isUpper("A#$"))