  
  [1X6 [33X[0;0YString and Text Utilities[133X[101X
  
  
  [1X6.1 [33X[0;0YText Utilities[133X[101X
  
  [33X[0;0YThis section describes some utility functions for handling texts within [5XGAP[105X.
  They  are  used by the functions in the [5XGAPDoc[105X package but may be useful for
  other  purposes  as  well.  We  start  with some variables containing useful
  strings and go on with functions for parsing and reformatting text.[133X
  
  [1X6.1-1 WHITESPACE[101X
  
  [33X[1;0Y[29X[2XWHITESPACE[102X[32X global variable[133X
  [33X[1;0Y[29X[2XCAPITALLETTERS[102X[32X global variable[133X
  [33X[1;0Y[29X[2XSMALLLETTERS[102X[32X global variable[133X
  [33X[1;0Y[29X[2XLETTERS[102X[32X global variable[133X
  [33X[1;0Y[29X[2XDIGITS[102X[32X global variable[133X
  [33X[1;0Y[29X[2XHEXDIGITS[102X[32X global variable[133X
  [33X[1;0Y[29X[2XBOXCHARS[102X[32X global variable[133X
  
  [33X[0;0YThese  variables  contain  sets  of  characters  which  are  useful for text
  processing. They are defined as follows.[133X
  
  [8X[10XWHITESPACE[110X[8X[108X
        [33X[0;6Y[10X" \n\t\r"[110X[133X
  
  [8X[10XCAPITALLETTERS[110X[8X[108X
        [33X[0;6Y[10X"ABCDEFGHIJKLMNOPQRSTUVWXYZ"[110X[133X
  
  [8X[10XSMALLLETTERS[110X[8X[108X
        [33X[0;6Y[10X"abcdefghijklmnopqrstuvwxyz"[110X[133X
  
  [8X[10XLETTERS[110X[8X[108X
        [33X[0;6Yconcatenation of [10XCAPITALLETTERS[110X and [10XSMALLLETTERS[110X[133X
  
  [8X[10XDIGITS[110X[8X[108X
        [33X[0;6Y[10X"0123456789"[110X[133X
  
  [8X[10XHEXDIGITS[110X[8X[108X
        [33X[0;6Y[10X"0123456789ABCDEFabcdef"[110X[133X
  
  [8X[10XBOXCHARS[110X[8X[108X
        [33X[0;6Y[10X"─│┌┬┐├┼┤└┴┘━┃┏┳┓┣╋┫┗┻┛═║╔╦╗╠╬╣╚╩╝"[110X , these are in UTF-8 encoding, the
        [10Xi[110X-th unicode character is [10XBOXCHARS{[3*i-2..3*i]}[110X.[133X
  
  [1X6.1-2 TextAttr[101X
  
  [33X[1;0Y[29X[2XTextAttr[102X[32X global variable[133X
  
  [33X[0;0YThe  record  [2XTextAttr[102X  contains  strings  which can be printed to change the
  terminal  attribute  for  the  following  characters.  This  only works with
  terminals  which  understand  basic ANSI escape sequences. Try the following
  example  to see if this is the case for the terminal you are using. It shows
  the  effect  of  the  foreground  and background color attributes and of the
  [10X.bold[110X, [10X.blink[110X, [10X.normal[110X, [10X.reverse[110X and [10X.underscore[110X which can partly be mixed.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[28Xextra := ["CSI", "reset", "delline", "home"];;[128X[104X
    [4X[28Xfor t in Difference(RecNames(TextAttr), extra) do[128X[104X
    [4X[28X  Print(TextAttr.(t), "TextAttr.", t, TextAttr.reset,"\n");[128X[104X
    [4X[28Xod;[128X[104X
  [4X[32X[104X
  
  [33X[0;0YThe  suggested  defaults for colors [10X0..7[110X are black, red, green, brown, blue,
  magenta,   cyan,  white.  But  this  may  be  different  for  your  terminal
  configuration.[133X
  
  [33X[0;0YThe  escape  sequence  [10X.delline[110X  deletes the content of the current line and
  [10X.home[110X moves the cursor to the beginning of the current line.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[28Xfor i in [1..5] do [128X[104X
    [4X[28X  Print(TextAttr.home, TextAttr.delline, String(i,-6), "\c"); [128X[104X
    [4X[28X  Sleep(1); [128X[104X
    [4X[28Xod;[128X[104X
  [4X[32X[104X
  
  [33X[0;0YWhenever you use this in some printing routines you should make it optional.
  Use   these   attributes  only  when  [10XUserPreference("UseColorsInTerminal");[110X
  returns [9Xtrue[109X.[133X
  
  [1X6.1-3 WrapTextAttribute[101X
  
  [33X[1;0Y[29X[2XWrapTextAttribute[102X( [3Xstr[103X, [3Xattr[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ya string with markup[133X
  
  [33X[0;0YThe  argument  [3Xstr[103X  must  be  a  text as [5XGAP[105X string, possibly with markup by
  escape  sequences  as  in  [2XTextAttr[102X  ([14X6.1-2[114X). This function returns a string
  which  is  wrapped by the escape sequences [3Xattr[103X and [10XTextAttr.reset[110X. It takes
  care  of  markup in the given string by appending [3Xattr[103X also after each given
  [10XTextAttr.reset[110X in [3Xstr[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xstr := Concatenation("XXX",TextAttr.2, "BLUB", TextAttr.reset,"YYY");[127X[104X
    [4X[28X"XXX\033[32mBLUB\033[0mYYY"[128X[104X
    [4X[25Xgap>[125X [27Xstr2 := WrapTextAttribute(str, TextAttr.1);[127X[104X
    [4X[28X"\033[31mXXX\033[32mBLUB\033[0m\033[31m\027YYY\033[0m"[128X[104X
    [4X[25Xgap>[125X [27Xstr3 := WrapTextAttribute(str, TextAttr.underscore);[127X[104X
    [4X[28X"\033[4mXXX\033[32mBLUB\033[0m\033[4m\027YYY\033[0m"[128X[104X
    [4X[25Xgap>[125X [27X# use Print(str); and so on to see how it looks like.[127X[104X
  [4X[32X[104X
  
  [1X6.1-4 FormatParagraph[101X
  
  [33X[1;0Y[29X[2XFormatParagraph[102X( [3Xstr[103X[, [3Xlen[103X][, [3Xflush[103X][, [3Xattr[103X][, [3Xwidthfun[103X] ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ythe formatted paragraph as string[133X
  
  [33X[0;0YThis  function  formats  a  text given in the string [3Xstr[103X as a paragraph. The
  optional arguments have the following meaning:[133X
  
  [8X[3Xlen[103X[8X[108X
        [33X[0;6Ythe  length of the lines of the formatted text, default is [10X78[110X (counted
        without  a  visible  length  of  the  strings  specified  in  the [3Xattr[103X
        argument)[133X
  
  [8X[3Xflush[103X[8X[108X
        [33X[0;6Ycan  be [10X"left"[110X, [10X"right"[110X, [10X"center"[110X or [10X"both"[110X, telling that lines should
        be  flushed  left,  flushed  right,  centered or left-right justified,
        respectively, default is [10X"both"[110X[133X
  
  [8X[3Xattr[103X[8X[108X
        [33X[0;6Yis  a  list  of  two  strings;  the  first is prepended and the second
        appended  to  each  line  of  the  result (can for example be used for
        indenting, [10X[" ", ""][110X, or some markup, [10X[TextAttr.bold, TextAttr.reset][110X,
        default is [10X["", ""][110X)[133X
  
  [8X[3Xwidthfun[103X[8X[108X
        [33X[0;6Ymust be a function which returns the display width of text in [3Xstr[103X. The
        default  is  [10XLength[110X assuming that each byte corresponds to a character
        of  width  one.  If  [3Xstr[103X  is  given  in  [10XUTF-8[110X  encoding  one  can use
        [2XWidthUTF8String[102X ([14X6.2-3[114X) here.[133X
  
  [33X[0;0YThis  function tries to handle markup with the escape sequences explained in
  [2XTextAttr[102X ([14X6.1-2[114X) correctly.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xstr := "One two three four five six seven eight nine ten eleven.";;[127X[104X
    [4X[25Xgap>[125X [27XPrint(FormatParagraph(str, 25, "left", ["/* ", " */"]));           [127X[104X
    [4X[28X/* One two three four five */[128X[104X
    [4X[28X/* six seven eight nine ten */[128X[104X
    [4X[28X/* eleven. */[128X[104X
  [4X[32X[104X
  
  [1X6.1-5 SubstitutionSublist[101X
  
  [33X[1;0Y[29X[2XSubstitutionSublist[102X( [3Xlist[103X, [3Xsublist[103X, [3Xnew[103X[, [3Xflag[103X] ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ythe changed list[133X
  
  [33X[0;0YThis  function  looks for (non-overlapping) occurrences of a sublist [3Xsublist[103X
  in  a  list  [3Xlist[103X (compare [2XPositionSublist[102X ([14XReference: PositionSublist[114X)) and
  returns a list where these are substituted with the list [3Xnew[103X.[133X
  
  [33X[0;0YThe  optional  argument [3Xflag[103X can either be [10X"all"[110X (this is the default if not
  given)  or [10X"one"[110X. In the second case only the first occurrence of [3Xsublist[103X is
  substituted.[133X
  
  [33X[0;0YIf  [3Xsublist[103X  does  not occur in [3Xlist[103X then [3Xlist[103X itself is returned (and not a
  [10XShallowCopy(list)[110X).[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XSubstitutionSublist("xababx", "ab", "a");[127X[104X
    [4X[28X"xaax"[128X[104X
  [4X[32X[104X
  
  [1X6.1-6 StripBeginEnd[101X
  
  [33X[1;0Y[29X[2XStripBeginEnd[102X( [3Xlist[103X, [3Xstrip[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ychanged string[133X
  
  [33X[0;0YHere [3Xlist[103X and [3Xstrip[103X must be lists. This function returns the sublist of list
  which does not contain the leading and trailing entries which are entries of
  [3Xstrip[103X. If the result is equal to [3Xlist[103X then [3Xlist[103X itself is returned.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XStripBeginEnd(" ,a, b,c,   ", ", ");[127X[104X
    [4X[28X"a, b,c"[128X[104X
  [4X[32X[104X
  
  [1X6.1-7 StripEscapeSequences[101X
  
  [33X[1;0Y[29X[2XStripEscapeSequences[102X( [3Xstr[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ystring without escape sequences[133X
  
  [33X[0;0YThis  function  returns  the string one gets from the string [3Xstr[103X by removing
  all  escape  sequences  which are explained in [2XTextAttr[102X ([14X6.1-2[114X). If [3Xstr[103X does
  not contain such a sequence then [3Xstr[103X itself is returned.[133X
  
  [1X6.1-8 RepeatedString[101X
  
  [33X[1;0Y[29X[2XRepeatedString[102X( [3Xc[103X, [3Xlen[103X ) [32X function[133X
  [33X[1;0Y[29X[2XRepeatedUTF8String[102X( [3Xc[103X, [3Xlen[103X ) [32X function[133X
  
  [33X[0;0YHere  [3Xc[103X  must  be  either  a character or a string and [3Xlen[103X is a non-negative
  number.  Then  [2XRepeatedString[102X  returns  a string of length [3Xlen[103X consisting of
  copies of [3Xc[103X.[133X
  
  [33X[0;0YIn  the variant [2XRepeatedUTF8String[102X the argument [3Xc[103X is considered as string in
  UTF-8 encoding, and it can also be specified as unicode string or character,
  see  [2XUnicode[102X  ([14X6.2-1[114X).  The  result  is a string in UTF-8 encoding which has
  visible width [3Xlen[103X as explained in [2XWidthUTF8String[102X ([14X6.2-3[114X).[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XRepeatedString('=',51);[127X[104X
    [4X[28X"==================================================="[128X[104X
    [4X[25Xgap>[125X [27XRepeatedString("*=",51);[127X[104X
    [4X[28X"*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*"[128X[104X
    [4X[25Xgap>[125X [27Xs := "bäh";;[127X[104X
    [4X[25Xgap>[125X [27Xenc := GAPInfo.TermEncoding;;[127X[104X
    [4X[25Xgap>[125X [27Xif enc <> "UTF-8" then s := Encode(Unicode(s, enc), "UTF-8"); fi;[127X[104X
    [4X[25Xgap>[125X [27Xl := RepeatedUTF8String(s, 8);;[127X[104X
    [4X[25Xgap>[125X [27Xu := Unicode(l, "UTF-8");;[127X[104X
    [4X[25Xgap>[125X [27XPrint(Encode(u, enc), "\n");[127X[104X
    [4X[28Xbähbähbä[128X[104X
  [4X[32X[104X
  
  [1X6.1-9 NumberDigits[101X
  
  [33X[1;0Y[29X[2XNumberDigits[102X( [3Xstr[103X, [3Xbase[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Yinteger[133X
  
  [33X[1;0Y[29X[2XDigitsNumber[102X( [3Xn[103X, [3Xbase[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ystring[133X
  
  [33X[0;0YThe  argument  [3Xstr[103X  of  [2XNumberDigits[102X  must be a string consisting only of an
  optional leading [10X'-'[110X and characters in [10X0123456789abcdefABCDEF[110X, describing an
  integer  in  base  [3Xbase[103X  with  [22X2  ≤  [3Xbase[103X  ≤  16[122X.  This function returns the
  corresponding integer.[133X
  
  [33X[0;0YThe function [2XDigitsNumber[102X does the reverse.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XNumberDigits("1A3F",16);[127X[104X
    [4X[28X6719[128X[104X
    [4X[25Xgap>[125X [27XDigitsNumber(6719, 16);[127X[104X
    [4X[28X"1A3F"[128X[104X
  [4X[32X[104X
  
  [1X6.1-10 LabelInt[101X
  
  [33X[1;0Y[29X[2XLabelInt[102X( [3Xn[103X, [3Xtype[103X, [3Xpre[103X, [3Xpost[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ystring[133X
  
  [33X[0;0YThe argument [3Xn[103X must be an integer in the range from 1 to 5000, while [3Xpre[103X and
  [3Xpost[103X must be strings.[133X
  
  [33X[0;0YThe  argument  [3Xtype[103X  can  be  one  of  [10X"Decimal"[110X, [10X"Roman"[110X, [10X"roman"[110X, [10X"Alpha"[110X,
  [10X"alpha"[110X.[133X
  
  [33X[0;0YThe  function  returns a string that starts with [3Xpre[103X, followed by a decimal,
  respectively   roman  number  or  alphanumerical  number  literal  (capital,
  respectively small letters), followed by [3Xpost[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XList([1,2,3,4,5,691], i-> LabelInt(i,"Decimal","","."));[127X[104X
    [4X[28X[ "1.", "2.", "3.", "4.", "5.", "691." ][128X[104X
    [4X[25Xgap>[125X [27XList([1,2,3,4,5,691], i-> LabelInt(i,"alpha","(",")"));[127X[104X
    [4X[28X[ "(a)", "(b)", "(c)", "(d)", "(e)", "(zo)" ][128X[104X
    [4X[25Xgap>[125X [27XList([1,2,3,4,5,691], i-> LabelInt(i,"alpha","(",")"));[127X[104X
    [4X[28X[ "(a)", "(b)", "(c)", "(d)", "(e)", "(zo)" ][128X[104X
    [4X[25Xgap>[125X [27XList([1,2,3,4,5,691], i-> LabelInt(i,"Alpha","",".)"));[127X[104X
    [4X[28X[ "A.)", "B.)", "C.)", "D.)", "E.)", "ZO.)" ][128X[104X
    [4X[25Xgap>[125X [27XList([1,2,3,4,5,691], i-> LabelInt(i,"roman","","."));[127X[104X
    [4X[28X[ "i.", "ii.", "iii.", "iv.", "v.", "dcxci." ][128X[104X
    [4X[25Xgap>[125X [27XList([1,2,3,4,5,691], i-> LabelInt(i,"Roman","",""));[127X[104X
    [4X[28X[ "I", "II", "III", "IV", "V", "DCXCI" ][128X[104X
  [4X[32X[104X
  
  [1X6.1-11 PositionMatchingDelimiter[101X
  
  [33X[1;0Y[29X[2XPositionMatchingDelimiter[102X( [3Xstr[103X, [3Xdelim[103X, [3Xpos[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Yposition as integer or [9Xfail[109X[133X
  
  [33X[0;0YHere  [3Xstr[103X must be a string and [3Xdelim[103X a string with two different characters.
  This  function searches the smallest position [10Xr[110X of the character [10X[3Xdelim[103X[10X[2][110X in
  [3Xstr[103X such that the number of occurrences of [10X[3Xdelim[103X[10X[2][110X in [3Xstr[103X between positions
  [10X[3Xpos[103X[10X+1[110X  and  [10Xr[110X is by one greater than the corresponding number of occurrences
  of [10X[3Xdelim[103X[10X[1][110X.[133X
  
  [33X[0;0YIf such an [10Xr[110X exists, it is returned. Otherwise [9Xfail[109X is returned.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XPositionMatchingDelimiter("{}x{ab{c}d}", "{}", 0);[127X[104X
    [4X[28Xfail[128X[104X
    [4X[25Xgap>[125X [27XPositionMatchingDelimiter("{}x{ab{c}d}", "{}", 1);[127X[104X
    [4X[28X2[128X[104X
    [4X[25Xgap>[125X [27XPositionMatchingDelimiter("{}x{ab{c}d}", "{}", 6);[127X[104X
    [4X[28X11[128X[104X
  [4X[32X[104X
  
  [1X6.1-12 WordsString[101X
  
  [33X[1;0Y[29X[2XWordsString[102X( [3Xstr[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ylist of strings containing the words[133X
  
  [33X[0;0YThis  returns  the  list  of  words  of a text stored in the string [3Xstr[103X. All
  non-letters are considered as word boundaries and are removed.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XWordsString("one_two \n    three!?");[127X[104X
    [4X[28X[ "one", "two", "three" ][128X[104X
  [4X[32X[104X
  
  [1X6.1-13 Base64String[101X
  
  [33X[1;0Y[29X[2XBase64String[102X( [3Xstr[103X ) [32X function[133X
  [33X[1;0Y[29X[2XStringBase64[102X( [3Xbstr[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ya string[133X
  
  [33X[0;0YThe  first  function  translates arbitrary binary data given as a GAP string
  into  a  [13Xbase 64[113X encoded string. This encoded string contains only printable
  ASCII  characters  and  is  used  in  various  data transfer protocols ([10XMIME[110X
  encoded  emails, weak password encryption, ...). We use the specification in
  RFC 2045 ([7Xhttp://tools.ietf.org/html/rfc2045[107X).[133X
  
  [33X[0;0YThe  second  function has the reverse functionality. Here we also accept the
  characters [10X-_[110X instead of [10X+/[110X as last two characters. Whitespace is ignored.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xb := Base64String("This is a secret!");[127X[104X
    [4X[28X"VGhpcyBpcyBhIHNlY3JldCEA="[128X[104X
    [4X[25Xgap>[125X [27XStringBase64(b);                       [127X[104X
    [4X[28X"This is a secret!"[128X[104X
  [4X[32X[104X
  
  
  [1X6.2 [33X[0;0YUnicode Strings[133X[101X
  
  [33X[0;0YThe  [5XGAPDoc[105X  package provides some tools to deal with unicode characters and
  strings.  These  can  be  used  for  recoding  text  strings between various
  encodings.[133X
  
  
  [1X6.2-1 [33X[0;0YUnicode Strings and Characters[133X[101X
  
  [33X[1;0Y[29X[2XUnicode[102X( [3Xlist[103X[, [3Xencoding[103X] ) [32X operation[133X
  [33X[1;0Y[29X[2XUChar[102X( [3Xnum[103X ) [32X operation[133X
  [33X[1;0Y[29X[2XIsUnicodeString[102X[32X filter[133X
  [33X[1;0Y[29X[2XIsUnicodeCharacter[102X[32X filter[133X
  [33X[1;0Y[29X[2XIntListUnicodeString[102X( [3Xustr[103X ) [32X function[133X
  
  [33X[0;0YUnicode characters are described by their [13Xcodepoint[113X, an integer in the range
  from [22X0[122X to [22X2^21-1[122X. For details about unicode, see [7Xhttp://www.unicode.org[107X.[133X
  
  [33X[0;0YThe  function  [2XUChar[102X  wraps  an  integer  [3Xnum[103X into a [5XGAP[105X object lying in the
  filter  [2XIsUnicodeCharacter[102X.  Use [10XInt[110X to get the codepoint back. The argument
  [3Xnum[103X  can  also be a [5XGAP[105X character which is then translated to an integer via
  [2XIntChar[102X ([14XReference: IntChar[114X).[133X
  
  [33X[0;0Y[2XUnicode[102X  produces  a  [5XGAP[105X  object  in  the filter [2XIsUnicodeString[102X. This is a
  wrapped  list  of  integers  for  the  unicode characters in the string. The
  function  [2XIntListUnicodeString[102X  gives access to this list of integers. Basic
  list  functionality  is  available for [2XIsUnicodeString[102X elements. The entries
  are in [2XIsUnicodeCharacter[102X. The argument [3Xlist[103X for [2XUnicode[102X is either a list of
  integers or a [5XGAP[105X string. In the latter case an [3Xencoding[103X can be specified as
  string, its default is [10X"UTF-8"[110X.[133X
  
  [33X[0;0YCurrently       supported      encodings      can      be      found      in
  [10XUNICODE_RECODE.NormalizedEncodings[110X  (ASCII,  ISO-8859-X, UTF-8 and aliases).
  The encoding [10X"XML"[110X means an ASCII encoding in which non-ASCII characters are
  specified  by  XML character entities. The encoding [10X"URL"[110X is for URL-encoded
  (also  called  percent-encoded  strings,  as specified in RFC 3986 (see here
  ([7Xhttp://www.ietf.org/rfc/rfc3986.txt[107X)).  The  listed  encodings  [10X"LaTeX"[110X and
  aliases  cannot  be  used with [2XUnicode[102X. See the operation [2XEncode[102X ([14X6.2-2[114X) for
  mapping a unicode string to a [5XGAP[105X string.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xustr := Unicode("a and \366", "latin1");[127X[104X
    [4X[28XUnicode("a and ö")[128X[104X
    [4X[25Xgap>[125X [27Xustr = Unicode("a and &#246;", "XML");  [127X[104X
    [4X[28Xtrue[128X[104X
    [4X[25Xgap>[125X [27XIntListUnicodeString(ustr);[127X[104X
    [4X[28X[ 97, 32, 97, 110, 100, 32, 246 ][128X[104X
    [4X[25Xgap>[125X [27Xustr[7];[127X[104X
    [4X[28X'ö'[128X[104X
  [4X[32X[104X
  
  [1X6.2-2 Encode[101X
  
  [33X[1;0Y[29X[2XEncode[102X( [3Xustr[103X[, [3Xencoding[103X] ) [32X operation[133X
  [6XReturns:[106X  [33X[0;10Ya [5XGAP[105X string[133X
  
  [33X[1;0Y[29X[2XSimplifiedUnicodeString[102X( [3Xustr[103X[, [3Xencoding[103X][, [3X"single"[103X] ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ya unicode string[133X
  
  [33X[1;0Y[29X[2XLowercaseUnicodeString[102X( [3Xustr[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ya unicode string[133X
  
  [33X[1;0Y[29X[2XUppercaseUnicodeString[102X( [3Xustr[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Ya unicode string[133X
  
  [33X[1;0Y[29X[2XLaTeXUnicodeTable[102X[32X global variable[133X
  [33X[1;0Y[29X[2XSimplifiedUnicodeTable[102X[32X global variable[133X
  [33X[1;0Y[29X[2XLowercaseUnicodeTable[102X[32X global variable[133X
  
  [33X[0;0YThe  operation  [2XEncode[102X translates a unicode string [3Xustr[103X into a [5XGAP[105X string in
  some specified [3Xencoding[103X. The default encoding is [10X"UTF-8"[110X.[133X
  
  [33X[0;0YSupported  encodings  can  be  found  in [10XUNICODE_RECODE.NormalizedEncodings[110X.
  Except  for some cases mentioned below characters which are not available in
  the target encoding are substituted by '?' characters.[133X
  
  [33X[0;0YIf  the  [3Xencoding[103X  is  [10X"URL"[110X (see [2XUnicode[102X ([14X6.2-1[114X)) then an optional argument
  [3Xencreserved[103X  can  be  given,  it must be a list of reserved characters which
  should be percent encoded; the default is to encode only the [10X%[110X character.[133X
  
  [33X[0;0YThe  encoding  [10X"LaTeX"[110X  substitutes  non-ASCII  characters and LaTeX special
  characters  by  LaTeX  code as given in an ordered list [10XLaTeXUnicodeTable[110X of
  pairs  [codepoint,  string].  If  you  have a unicode character for which no
  substitution  is  contained  in  that  list,  you will get a warning and the
  translation  is  [10XUnicode(nr)[110X.  In  this  case  find a substitution and add a
  corresponding  [codepoint,  string]  pair  to [10XLaTeXUnicodeTable[110X using [2XAddSet[102X
  ([14XReference:  AddSet[114X).  Also,  please,  tell  the  [5XGAPDoc[105X  authors about your
  addition,  such  that we can extend the list [10XLaTeXUnicodeTable[110X. (Most of the
  initial  entries  were  generated  from lists in the TeX projects encTeX and
  [10Xucs[110X.) There are some variants of this encoding:[133X
  
  [33X[0;0Y[10X"LaTeXleavemarkup"[110X  does  the same translations for non-ASCII characters but
  leaves the LaTeX special characters (e.g., any LaTeX commands) as they are.[133X
  
  [33X[0;0Y[10X"LaTeXUTF8"[110X  does  not  give  a  warning  about  unicode  characters without
  explicit  translation,  instead  it  translates  the  character to its [10XUTF-8[110X
  encoding.  Make  sure  to  setup  your  LaTeX  document  such that all these
  characters are understood.[133X
  
  [33X[0;0Y[10X"LaTeXUTF8leavemarkup"[110X is a combination of the last two variants.[133X
  
  [33X[0;0YNote  that the [10X"LaTeX"[110X encoding can only be used with [2XEncode[102X but not for the
  opposite  translation  with  [2XUnicode[102X  ([14X6.2-1[114X)  (which  would  need  far  too
  complicated heuristics).[133X
  
  [33X[0;0YThe   function  [2XSimplifiedUnicodeString[102X  can  be  used  to  substitute  many
  non-ASCII  characters  by  related  ASCII  characters or strings (e.g., by a
  corresponding  character  without accents). The argument [3Xustr[103X and the result
  are  unicode  strings,  if [3Xencoding[103X is [10X"ASCII"[110X then all non-ASCII characters
  are  translated,  otherwise  only  the  non-latin1 characters. If the string
  [10X"single"[110X  in  an argument then only substitutions are considered which don't
  make  the result string longer. The translations are stored in a sorted list
  [10XSimplifiedUnicodeTable[110X.  Its  entries  are  of  the form [10X[codepoint, trans1,
  trans2,  ...][110X.  Here [10Xtrans1[110X and so on is either an integer for the codepoint
  of  a  substitution  character or it is a list of codepoint integers. If you
  are missing characters in this list and know a sensible ASCII approximation,
  then  add  an  entry  (with  [2XAddSet[102X ([14XReference: AddSet[114X)) and tell the [5XGAPDoc[105X
  authors  about it. (The initial content of [10XSimplifiedUnicodeTable[110X was mainly
  generated from the [21X[10Xtranstab[110X[121X tables by Markus Kuhn.)[133X
  
  [33X[0;0YThe  function  [2XLowercaseUnicodeString[102X  gets and returns a unicode string and
  translates  each uppercase character to its corresponding lowercase version.
  This  function  uses  a  list  [10XLowercaseUnicodeTable[110X  of  pairs of codepoint
  integers.  This  list  was generated using the file [11XUnicodeData.txt[111X from the
  unicode definition (field 14 in each row).[133X
  
  [33X[0;0YThe   function   [2XUppercaseUnicodeString[102X  does  the  similar  translation  to
  uppercase characters.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xustr := Unicode("a and &#246;", "XML");[127X[104X
    [4X[28XUnicode("a and ö")[128X[104X
    [4X[25Xgap>[125X [27XSimplifiedUnicodeString(ustr, "ASCII");[127X[104X
    [4X[28XUnicode("a and oe")[128X[104X
    [4X[25Xgap>[125X [27XSimplifiedUnicodeString(ustr, "ASCII", "single");[127X[104X
    [4X[28XUnicode("a and o")[128X[104X
    [4X[25Xgap>[125X [27Xustr2 := UppercaseUnicodeString(ustr);;[127X[104X
    [4X[25Xgap>[125X [27XPrint(Encode(ustr2, GAPInfo.TermEncoding), "\n");[127X[104X
    [4X[28XA AND Ö[128X[104X
  [4X[32X[104X
  
  
  [1X6.2-3 [33X[0;0YLengths of UTF-8 strings[133X[101X
  
  [33X[1;0Y[29X[2XWidthUTF8String[102X( [3Xstr[103X ) [32X function[133X
  [33X[1;0Y[29X[2XNrCharsUTF8String[102X( [3Xstr[103X ) [32X function[133X
  [6XReturns:[106X  [33X[0;10Yan integer[133X
  
  [33X[0;0YLet [3Xstr[103X be a [5XGAP[105X string with text in UTF-8 encoding. There are three [21Xlengths[121X
  of  such  a  string  which  must  be  distinguished.  The  operation  [2XLength[102X
  ([14XReference:  Length[114X)  returns the number of bytes and so the memory occupied
  by  [3Xstr[103X.  The  function  [2XNrCharsUTF8String[102X  returns  the  number  of unicode
  characters in [3Xstr[103X, that is the length of [10XUnicode([3Xstr[103X[10X)[110X.[133X
  
  [33X[0;0YIn  many  applications  the function [2XWidthUTF8String[102X is more interesting, it
  returns the number of columns needed by the string if printed to a terminal.
  This   takes  into  account  that  some  unicode  characters  are  combining
  characters  and that there are wide characters which need two columns (e.g.,
  for  Chinese  or Japanese). (To be precise: This implementation assumes that
  there are no control characters in [3Xstr[103X and uses the character width returned
  by the [10Xwcwidth[110X function in the GNU C-library called with UTF-8 locale.)[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27X# A, German umlaut u, B, zero width space, C, newline[127X[104X
    [4X[25Xgap>[125X [27Xstr := Encode( Unicode( "A&#xFC;B&#x200B;C\n", "XML" ) );;[127X[104X
    [4X[25Xgap>[125X [27XPrint(str);[127X[104X
    [4X[28XAüB​C[128X[104X
    [4X[25Xgap>[125X [27X# umlaut u needs two bytes and the zero width space three[127X[104X
    [4X[25Xgap>[125X [27XLength(str);[127X[104X
    [4X[28X9[128X[104X
    [4X[25Xgap>[125X [27XNrCharsUTF8String(str);[127X[104X
    [4X[28X6[128X[104X
    [4X[25Xgap>[125X [27X# zero width space and newline don't contribute to width[127X[104X
    [4X[25Xgap>[125X [27XWidthUTF8String(str);[127X[104X
    [4X[28X4[128X[104X
  [4X[32X[104X
  
  [1X6.2-4 InitialSubstringUTF8String[101X
  
  [33X[1;0Y[29X[2XInitialSubstringUTF8String[102X( [3Xstr[103X, [3Xmaxwidth[103X[, [3Xsuf[103X] ) [32X function[133X
  [6XReturns:[106X  [33X[0;10YUTF-8 encoded string[133X
  
  [33X[0;0YThe  arguments  [3Xstr[103X  and  [3Xsuf[103X  each  must be a [5XGAP[105X string with text in UTF-8
  encoding  or  a unicode string. The argument [3Xsuf[103X is optional and its default
  value  is  the empty string. If the visible width of [3Xstr[103X is at most [3Xmaxwidth[103X
  then [3Xstr[103X is returned as UTF-8 encoded [5XGAP[105X string. Otherwise, [3Xsuf[103X is appended
  to the maximal initial substring of [3Xstr[103X such that the total visible width of
  the result is at most [3Xmaxwidth[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27X# A, German umlaut u, B, zero width space, C, newline[127X[104X
    [4X[25Xgap>[125X [27Xstr := Encode( Unicode( "A&#xFC;B&#x200B;C\n", "XML" ) );;[127X[104X
    [4X[25Xgap>[125X [27Xini := InitialSubstringUTF8String(str, 3);;[127X[104X
    [4X[25Xgap>[125X [27XWidthUTF8String(ini);[127X[104X
    [4X[28X3[128X[104X
    [4X[25Xgap>[125X [27XIntListUnicodeString(Unicode(ini));[127X[104X
    [4X[28X[ 65, 252, 66, 8203 ][128X[104X
    [4X[25Xgap>[125X [27Xl := Unicode([ 23380, 22827, 23376 ] );; # three chars of width 2[127X[104X
    [4X[25Xgap>[125X [27Xs := InitialSubstringUTF8String(l, 4, "*");;[127X[104X
    [4X[25Xgap>[125X [27XWidthUTF8String(s);[127X[104X
    [4X[28X3[128X[104X
  [4X[32X[104X
  
  
  [1X6.3 [33X[0;0YPrint Utilities[133X[101X
  
  [33X[0;0YThe  following  printing  utilities  turned out to be useful for interactive
  work  with  texts  in [5XGAP[105X. But they are more general and so we document them
  here.[133X
  
  [1X6.3-1 PrintTo1[101X
  
  [33X[1;0Y[29X[2XPrintTo1[102X( [3Xfilename[103X, [3Xfun[103X ) [32X function[133X
  [33X[1;0Y[29X[2XAppendTo1[102X( [3Xfilename[103X, [3Xfun[103X ) [32X function[133X
  
  [33X[0;0YThe  argument  [3Xfun[103X must be a function without arguments. Everything which is
  printed  by  a call [3Xfun()[103X is printed into the file [3Xfilename[103X. As with [2XPrintTo[102X
  ([14XReference:  PrintTo[114X)  and [2XAppendTo[102X ([14XReference: AppendTo[114X) this overwrites or
  appends to, respectively, a previous content of [3Xfilename[103X.[133X
  
  [33X[0;0YThese functions can be particularly efficient when many small pieces of text
  shall  be  written  to  a file, because no multiple reopening of the file is
  necessary.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xf := function() local i; [127X[104X
    [4X[25X>[125X [27X  for i in [1..100000] do Print(i, "\n"); od; end;; [127X[104X
    [4X[25Xgap>[125X [27XPrintTo1("nonsense", f); # now check the local file `nonsense'[127X[104X
  [4X[32X[104X
  
  [1X6.3-2 StringPrint[101X
  
  [33X[1;0Y[29X[2XStringPrint[102X( [3Xobj1[103X[, [3Xobj2[103X[, [3X...[103X]] ) [32X function[133X
  [33X[1;0Y[29X[2XStringView[102X( [3Xobj[103X ) [32X function[133X
  
  [33X[0;0YThese  functions return a string containing the output of a [10XPrint[110X or [10XViewObj[110X
  call with the same arguments.[133X
  
  [33X[0;0YThis should be considered as a (temporary?) hack. It would be better to have
  [2XString[102X ([14XReference: String[114X) methods for all [5XGAP[105X objects and to have a generic
  [2XPrint[102X ([14XReference: Print[114X)-function which just interprets these strings.[133X
  
  [1X6.3-3 PrintFormattedString[101X
  
  [33X[1;0Y[29X[2XPrintFormattedString[102X( [3Xstr[103X ) [32X function[133X
  
  [33X[0;0YThis  function prints a string [3Xstr[103X. The difference to [10XPrint(str);[110X is that no
  additional  line breaks are introduced by [5XGAP[105X's standard printing mechanism.
  This  can  be  used  to print lines which are longer than the current screen
  width. In particular one can print text which contains escape sequences like
  those  explained  in  [2XTextAttr[102X ([14X6.1-2[114X), where lines may have more characters
  than [13Xvisible characters[113X.[133X
  
  [1X6.3-4 Page[101X
  
  [33X[1;0Y[29X[2XPage[102X( [3X...[103X ) [32X function[133X
  [33X[1;0Y[29X[2XPageDisplay[102X( [3Xobj[103X ) [32X function[133X
  
  [33X[0;0YThese  functions  are  similar  to  [2XPrint[102X  ([14XReference:  Print[114X)  and  [2XDisplay[102X
  ([14XReference: Display[114X), respectively. The difference is that the output is not
  sent  directly to the screen, but is piped into the current pager; see [2XPager[102X
  ([14XReference: Pager[114X).[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XPage([1..1421]+0);[127X[104X
    [4X[25Xgap>[125X [27XPageDisplay(CharacterTable("Symmetric", 14));[127X[104X
  [4X[32X[104X
  
  [1X6.3-5 StringFile[101X
  
  [33X[1;0Y[29X[2XStringFile[102X( [3Xfilename[103X ) [32X function[133X
  [33X[1;0Y[29X[2XFileString[102X( [3Xfilename[103X, [3Xstr[103X[, [3Xappend[103X] ) [32X function[133X
  
  [33X[0;0YThe  function  [2XStringFile[102X  returns the content of file [3Xfilename[103X as a string.
  This  works  efficiently with arbitrary (binary or text) files. If something
  went wrong, this function returns [9Xfail[109X.[133X
  
  [33X[0;0YConversely  the  function [2XFileString[102X writes the content of a string [3Xstr[103X into
  the file [3Xfilename[103X. If the optional third argument [3Xappend[103X is given and equals
  [9Xtrue[109X  then  the  content  of [3Xstr[103X is appended to the file. Otherwise previous
  content  of  the  file is deleted. This function returns the number of bytes
  written or [9Xfail[109X if something went wrong.[133X
  
  [33X[0;0YBoth functions are quite efficient, even with large files.[133X
  
