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# 78. stringproc

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## 78.1 Introduction to string processing

`stringproc.lisp` enlarges Maximas capabilities of working with strings and adds some useful functions for file in/output.

For questions and bugs please mail to van.nek at arcor.de .

In Maxima a string is easily constructed by typing "text". `stringp` tests for strings.

    (%i1) m: "text";
    (%o1)                         text
    (%i2) stringp(m);
    (%o2)                         true

Characters are represented as strings of length 1. These are not Lisp characters. Tests can be done with `charp` (respectively `lcharp` and conversion from Lisp to Maxima characters with `cunlisp`).

    (%i1) c: "e";
    (%o1)                           e
    (%i2) [charp(c),lcharp(c)];
    (%o2)                     [true, false]
    (%i3) supcase(c);
    (%o3)                           E
    (%i4) charp(%);
    (%o4)                         true

All functions in `stringproc.lisp` that return characters, return Maxima-characters. Due to the fact, that the introduced characters are strings of length 1, you can use a lot of string functions also for characters. As seen, `supcase` is one example.

It is important to know, that the first character in a Maxima-string is at position 1. This is designed due to the fact that the first element in a Maxima-list is at position 1 too. See definitions of `charat` and `charlist` for examples.

In applications string-functions are often used when working with files. You will find some useful stream- and print-functions in `stringproc.lisp`. The following example shows some of the here introduced functions at work.

Example:

`openw` returns an output stream to a file, `printf` then allows formatted writing to this file. See `printf` for details.

    (%i1) s: openw("E:/file.txt");
    (%o1)                    #<output stream E:/file.txt>
    (%i2) for n:0 thru 10 do printf( s, "~d ", fib(n) );
    (%o2)                                done
    (%i3) printf( s, "~%~d ~f ~a ~a ~f ~e ~a~%",
                  42,1.234,sqrt(2),%pi,1.0e-2,1.0e-2,1.0b-2 );
    (%o3)                                false
    (%i4) close(s);
    (%o4)                                true

After closing the stream you can open it again, this time with input direction. `readline` returns the entire line as one string. The `stringproc` package now offers a lot of functions for manipulating strings. Tokenizing can be done by `split` or `tokens`.

    (%i5) s: openr("E:/file.txt");
    (%o5)                     #<input stream E:/file.txt>
    (%i6) readline(s);
    (%o6)                     0 1 1 2 3 5 8 13 21 34 55
    (%i7) line: readline(s);
    (%o7)               42 1.234 sqrt(2) %pi 0.01 1.0E-2 1.0b-2
    (%i8) list: tokens(line);
    (%o8)           [42, 1.234, sqrt(2), %pi, 0.01, 1.0E-2, 1.0b-2]
    (%i9) map( parse_string, list );
    (%o9)            [42, 1.234, sqrt(2), %pi, 0.01, 0.01, 1.0b-2]
    (%i10) float(%);
    (%o10) [42.0, 1.234, 1.414213562373095, 3.141592653589793, 0.01,
                                                         0.01, 0.01]
    (%i11) readline(s);
    (%o11)                               false
    (%i12) close(s)$

`readline` returns `false` when the end of file occurs.

·

@ref{Category: Strings} · @ref{Category: Share packages} · @ref{Category: Package stringproc}

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## 78.2 Functions and Variables for input and output

Example:

    (%i1) s: openw("E:/file.txt");
    (%o1)                     #<output stream E:/file.txt>
    (%i2) control:
    "~2tAn atom: ~20t~a~%~2tand a list: ~20t~{~r ~}~%~2t\
    and an integer: ~20t~d~%"$
    (%i3) printf( s,control, 'true,[1,2,3],42 )$
    (%o3)                                false
    (%i4) close(s);
    (%o4)                                true
    (%i5) s: openr("E:/file.txt");
    (%o5)                     #<input stream E:/file.txt>
    (%i6) while stringp( tmp:readline(s) ) do print(tmp)$
      An atom:          true
      and a list:       one two three
      and an integer:   42
    (%i7) close(s)$

Function: close (stream)

  Closes stream and returns `true` if stream had been open.

  ·

  @ref{Category: File input} · @ref{Category: File output} · @ref{Category: Package stringproc}

Function: flength (stream)

  Returns the number of elements in stream.

  ·

  @ref{Category: File input} · @ref{Category: File output} · @ref{Category: Package stringproc}

Function: fposition (stream)
Function: fposition (stream, pos)

  Returns the current position in stream, if pos is not used. If pos is used, `fposition` sets the position in stream. pos has to be a positive number, the first element in stream is in position 1.

  ·

  @ref{Category: File input} · @ref{Category: File output} · @ref{Category: Package stringproc}

Function: freshline ()
Function: freshline (stream)

  Writes a new line (to stream), if the position is not at the beginning of a line. See also `newline`.

  ·

  @ref{Category: File output} · @ref{Category: Package stringproc}

Function: newline ()
Function: newline (stream)

  Writes a new line (to stream). See `sprint` for an example of using `newline()`. Note that there are some cases, where `newline()` does not work as expected.

  ·

  @ref{Category: File output} · @ref{Category: Package stringproc}

Function: opena (file)

  Returns an output stream to file. If an existing file is opened, `opena` appends elements at the end of file.

  ·

  @ref{Category: File output} · @ref{Category: Package stringproc}

Function: openr (file)

  Returns an input stream to file. If file does not exist, it will be created.

  ·

  @ref{Category: File input} · @ref{Category: Package stringproc}

Function: openw (file)

  Returns an output stream to file. If file does not exist, it will be created. If an existing file is opened, `openw` destructively modifies file.

  ·

  @ref{Category: File output} · @ref{Category: Package stringproc}

Function: printf (dest, string)
Function: printf (dest, string, expr_1, ..., expr_n)

  Makes the Common Lisp function FORMAT available in Maxima. (From gcl.info: "format produces formatted output by outputting the characters of control-string string and observing that a tilde introduces a directive. The character after the tilde, possibly preceded by prefix parameters and modifiers, specifies what kind of formatting is desired. Most directives use one or more elements of args to create their output.")

  The following description and the examples may give an idea of using `printf`. See a Lisp reference for more information.

         ~%       new line
         ~&       fresh line
         ~t       tab
         ~$       monetary
         ~d       decimal integer
         ~b       binary integer
         ~o       octal integer
         ~x       hexadecimal integer
         ~br      base-b integer
         ~r       spell an integer
         ~p       plural
         ~f       floating point
         ~e       scientific notation
         ~g       ~f or ~e, depending upon magnitude
         ~h       bigfloat
         ~a       uses Maxima function string
         ~s       like ~a, but output enclosed in "double quotes"
         ~~       ~
         ~<       justification, ~> terminates
         ~(       case conversion, ~) terminates
         ~[       selection, ~] terminates
         ~{       iteration, ~} terminates

  Note that the selection directive `~[` is zero-indexed. Also note that the directive ~* is not supported.

      (%i1) printf( false, "~a ~a ~4f ~a ~@r",
                    "String",sym,bound,sqrt(12),144), bound = 1.234;
      (%o1)                 String sym 1.23 2*sqrt(3) CXLIV
      (%i2) printf( false,"~{~a ~}",["one",2,"THREE"] );
      (%o2)                          one 2 THREE
      (%i3) printf(true,"~{~{~9,1f ~}~%~}",mat ),
                mat = args(matrix([1.1,2,3.33],[4,5,6],[7,8.88,9]))$
            1.1       2.0       3.3
            4.0       5.0       6.0
            7.0       8.9       9.0
      (%i4) control: "~:(~r~) bird~p ~[is~;are~] singing."$
      (%i5) printf( false,control, n,n,if n=1 then 0 else 1 ), n=2;
      (%o5)                    Two birds are singing.

  If dest is a stream or `true`, then `printf` returns `false`. Otherwise, `printf` returns a string containing the output.

  ·

  @ref{Category: File output} · @ref{Category: Package stringproc}

Function: readline (stream)

  Returns a string containing the characters from the current position in stream up to the end of the line or false if the end of the file is encountered.

  ·

  @ref{Category: File input} · @ref{Category: Package stringproc}

Function: sprint (expr_1, …, expr_n)

  Evaluates and displays its arguments one after the other `on a line' starting at the leftmost position. The numbers are printed with the '-' right next to the number, and it disregards line length. `newline()`, which will be autoloaded from `stringproc.lisp` might be useful, if you whish to place intermediate line breaking.

  Example:

      (%i1) for n:0 thru 19 do sprint( fib(n) )$
      0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181
      (%i2) for n:0 thru 22 do (
               sprint(fib(n)), if mod(n,10)=9 then newline() )$
      0 1 1 2 3 5 8 13 21 34
      55 89 144 233 377 610 987 1597 2584 4181
      6765 10946 17711

  ·

  @ref{Category: Package stringproc}

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## 78.3 Functions and Variables for characters

Function: alphacharp (char)

  Returns `true` if char is an alphabetic character.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: alphanumericp (char)

  Returns `true` if char is an alphabetic character or a digit.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: ascii (int)

  Returns the character corresponding to the ASCII number int. ( -1 < int < 256 )

      (%i1) for n from 0 thru 255 do (
         tmp: ascii(n), if alphacharp(tmp) then sprint(tmp),
            if n=96 then newline() )$
      A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
      a b c d e f g h i j k l m n o p q r s t u v w x y z

  ·

  @ref{Category: Package stringproc}

Function: cequal (char_1, char_2)

  Returns `true` if char_1 and char_2 are the same.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: cequalignore (char_1, char_2)

  Like `cequal` but ignores case.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: cgreaterp (char_1, char_2)

  Returns `true` if the ASCII number of char_1 is greater than the number of char_2.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: cgreaterpignore (char_1, char_2)

  Like `cgreaterp` but ignores case.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: charp (obj)

  Returns `true` if obj is a Maxima-character. See introduction for example.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: cint (char)

  Returns the ASCII number of char.

  ·

  @ref{Category: Package stringproc}

Function: clessp (char_1, char_2)

  Returns `true` if the ASCII number of char_1 is less than the number of char_2.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: clesspignore (char_1, char_2)

  Like `clessp` but ignores case.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: constituent (char)

  Returns `true` if char is a graphic character and not the space character. A graphic character is a character one can see, plus the space character. (`constituent` is defined by Paul Graham, ANSI Common Lisp, 1996, page 67.)

      (%i1) for n from 0 thru 255 do (
      tmp: ascii(n), if constituent(tmp) then sprint(tmp) )$
      ! " #  %  ' ( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ; < = > ? @ A B
      C D E F G H I J K L M N O P Q R S T U V W X Y Z [ \ ] ^ _ ` a b c
      d e f g h i j k l m n o p q r s t u v w x y z { | } ~

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: cunlisp (lisp_char)

  Converts a Lisp-character into a Maxima-character. (You won't need it.)

  ·

  @ref{Category: Package stringproc}

Function: digitcharp (char)

  Returns `true` if char is a digit.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: lcharp (obj)

  Returns `true` if obj is a Lisp-character. (You won't need it.)

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: lowercasep (char)

  Returns `true` if char is a lowercase character.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Variable: newline

  The newline character.

  ·

  @ref{Category: Global variables} · @ref{Category: Package stringproc}

Variable: space

  The space character.

  ·

  @ref{Category: Global variables} · @ref{Category: Package stringproc}

Variable: tab

  The tab character.

  ·

  @ref{Category: Global variables} · @ref{Category: Package stringproc}

Function: uppercasep (char)

  Returns `true` if char is an uppercase character.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

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## 78.4 Functions and Variables for strings

Function: stringp (obj)

  Returns `true` if obj is a string. See introduction for example.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: charat (string, n)

  Returns the n-th character of string. The first character in string is returned with n = 1.

      (%i1) charat("Lisp",1);
      (%o1)                           L

  ·

  @ref{Category: Package stringproc}

Function: charlist (string)

  Returns the list of all characters in string.

      (%i1) charlist("Lisp");
      (%o1)                     [L, i, s, p]
      (%i2) %[1];
      (%o2)                           L

  ·

  @ref{Category: Package stringproc}

Function: eval_string (str)

  Parse the string str as a Maxima expression and evaluate it. The string str may or may not have a terminator (dollar sign `$` or semicolon `;`). Only the first expression is parsed and evaluated, if there is more than one.

  Complain if str is not a string.

  Examples:

      (%i1) eval_string ("foo: 42; bar: foo^2 + baz");
      (%o1)                       42
      (%i2) eval_string ("(foo: 42, bar: foo^2 + baz)");
      (%o2)                   baz + 1764

  See also `parse_string`.

  ·

  @ref{Category: Package stringproc}

Function: parse_string (str)

  Parse the string str as a Maxima expression (do not evaluate it). The string str may or may not have a terminator (dollar sign `$` or semicolon `;`). Only the first expression is parsed, if there is more than one.

  Complain if str is not a string.

  Examples:

      (%i1) parse_string ("foo: 42; bar: foo^2 + baz");
      (%o1)                    foo : 42
      (%i2) parse_string ("(foo: 42, bar: foo^2 + baz)");
                                         2
      (%o2)          (foo : 42, bar : foo  + baz)

  See also `eval_string`.

  ·

  @ref{Category: Package stringproc}

Function: scopy (string)

  Returns a copy of string as a new string.

  ·

  @ref{Category: Package stringproc}

Function: sdowncase (string)
Function: sdowncase (string, start)
Function: sdowncase (string, start, end)

  Like `supcase`, but uppercase characters are converted to lowercase.

  ·

  @ref{Category: Package stringproc}

Function: sequal (string_1, string_2)

  Returns `true` if string_1 and string_2 are the same length and contain the same characters.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: sequalignore (string_1, string_2)

  Like `sequal` but ignores case.

  ·

  @ref{Category: Predicate functions} · @ref{Category: Package stringproc}

Function: sexplode (string)

  `sexplode` is an alias for function `charlist`.

  ·

  @ref{Category: Package stringproc}

Function: simplode (list)
Function: simplode (list, delim)

  `simplode` takes a list of expressions and concatenates them into a string. If no delimiter delim is specified, `simplode` uses no delimiter. delim can be any string.

      (%i1) simplode(["xx[",3,"]:",expand((x+y)^3)]);
      (%o1)             xx[3]:y^3+3*x*y^2+3*x^2*y+x^3
      (%i2) simplode( sexplode("stars")," * " );
      (%o2)                   s * t * a * r * s
      (%i3) simplode( ["One","more","coffee."]," " );
      (%o3)                   One more coffee.

  ·

  @ref{Category: Package stringproc}

Function: sinsert (seq, string, pos)

  Returns a string that is a concatenation of `substring (string, 1, pos - 1)`, the string seq and `substring (string, pos)`. Note that the first character in string is in position 1.

      (%i1) s: "A submarine."$
      (%i2) concat( substring(s,1,3),"yellow ",substring(s,3) );
      (%o2)                  A yellow submarine.
      (%i3) sinsert("hollow ",s,3);
      (%o3)                  A hollow submarine.

  ·

  @ref{Category: Package stringproc}

Function: sinvertcase (string)
Function: sinvertcase (string, start)
Function: sinvertcase (string, start, end)

  Returns string except that each character from position start to end is inverted. If end is not given, all characters from start to the end of string are replaced.

      (%i1) sinvertcase("sInvertCase");
      (%o1)                      SiNVERTcASE

  ·

  @ref{Category: Package stringproc}

Function: slength (string)

  Returns the number of characters in string.

  ·

  @ref{Category: Package stringproc}

Function: smake (num, char)

  Returns a new string with a number of num characters char.

      (%i1) smake(3,"w");
      (%o1)                          www

  ·

  @ref{Category: Package stringproc}

Function: smismatch (string_1, string_2)
Function: smismatch (string_1, string_2, test)

  Returns the position of the first character of string_1 at which string_1 and string_2 differ or `false`. Default test function for matching is `sequal`. If `smismatch` should ignore case, use `sequalignore` as test.

      (%i1) smismatch("seven","seventh");
      (%o1)                           6

  ·

  @ref{Category: Package stringproc}

Function: split (string)
Function: split (string, delim)
Function: split (string, delim, multiple)

  Returns the list of all tokens in string. Each token is an unparsed string. `split` uses delim as delimiter. If delim is not given, the space character is the default delimiter. multiple is a boolean variable with `true` by default. Multiple delimiters are read as one. This is useful if tabs are saved as multiple space characters. If multiple is set to `false`, each delimiter is noted.

      (%i1) split("1.2   2.3   3.4   4.5");
      (%o1)                 [1.2, 2.3, 3.4, 4.5]
      (%i2) split("first;;third;fourth",";",false);
      (%o2)               [first, , third, fourth]

  ·

  @ref{Category: Package stringproc}

Function: sposition (char, string)

  Returns the position of the first character in string which matches char. The first character in string is in position 1. For matching characters ignoring case see `ssearch`.

  ·

  @ref{Category: Package stringproc}

Function: sremove (seq, string)
Function: sremove (seq, string, test)
Function: sremove (seq, string, test, start)
Function: sremove (seq, string, test, start, end)

  Returns a string like string but without all substrings matching seq. Default test function for matching is `sequal`. If `sremove` should ignore case while searching for seq, use `sequalignore` as test. Use start and end to limit searching. Note that the first character in string is in position 1.

      (%i1) sremove("n't","I don't like coffee.");
      (%o1)                   I do like coffee.
      (%i2) sremove ("DO ",%,'sequalignore);
      (%o2)                    I like coffee.

  ·

  @ref{Category: Package stringproc}

Function: sremovefirst (seq, string)
Function: sremovefirst (seq, string, test)
Function: sremovefirst (seq, string, test, start)
Function: sremovefirst (seq, string, test, start, end)

  Like `sremove` except that only the first substring that matches `seq` is removed.

  ·

  @ref{Category: Package stringproc}

Function: sreverse (string)

  Returns a string with all the characters of string in reverse order.

  ·

  @ref{Category: Package stringproc}

Function: ssearch (seq, string)
Function: ssearch (seq, string, test)
Function: ssearch (seq, string, test, start)
Function: ssearch (seq, string, test, start, end)

  Returns the position of the first substring of string that matches the string seq. Default test function for matching is `sequal`. If `ssearch` should ignore case, use `sequalignore` as test. Use start and end to limit searching. Note that the first character in string is in position 1.

      (%i1) ssearch("~s","~{~S ~}~%",'sequalignore);
      (%o1)                                  4

  ·

  @ref{Category: Package stringproc}

Function: ssort (string)
Function: ssort (string, test)

  Returns a string that contains all characters from string in an order such there are no two successive characters c and d such that `test (c, d)` is `false` and `test (d, c)` is `true`. Default test function for sorting is clessp. The set of test functions is `{clessp, clesspignore, cgreaterp, cgreaterpignore, cequal, cequalignore}`.

      (%i1) ssort("I don't like Mondays.");
      (%o1)                    '.IMaddeiklnnoosty
      (%i2) ssort("I don't like Mondays.",'cgreaterpignore);
      (%o2)                 ytsoonnMlkIiedda.'

  ·

  @ref{Category: Package stringproc}

Function: ssubst (new, old, string)
Function: ssubst (new, old, string, test)
Function: ssubst (new, old, string, test, start)
Function: ssubst (new, old, string, test, start, end)

  Returns a string like string except that all substrings matching old are replaced by new. old and new need not to be of the same length. Default test function for matching is `sequal`. If `ssubst` should ignore case while searching for old, use `sequalignore` as test. Use start and end to limit searching. Note that the first character in string is in position 1.

      (%i1) ssubst("like","hate","I hate Thai food. I hate green tea.");
      (%o1)          I like Thai food. I like green tea.
      (%i2) ssubst("Indian","thai",%,'sequalignore,8,12);
      (%o2)         I like Indian food. I like green tea.

  ·

  @ref{Category: Package stringproc}

Function: ssubstfirst (new, old, string)
Function: ssubstfirst (new, old, string, test)
Function: ssubstfirst (new, old, string, test, start)
Function: ssubstfirst (new, old, string, test, start, end)

  Like `subst` except that only the first substring that matches old is replaced.

  ·

  @ref{Category: Package stringproc}

Function: strim (seq,string)

  Returns a string like string, but with all characters that appear in seq removed from both ends.

      (%i1) "/* comment */"$
      (%i2) strim(" /*",%);
      (%o2)                        comment
      (%i3) slength(%);
      (%o3)                           7

  ·

  @ref{Category: Package stringproc}

Function: striml (seq, string)

  Like `strim` except that only the left end of string is trimmed.

  ·

  @ref{Category: Package stringproc}

Function: strimr (seq, string)

  Like `strim` except that only the right end of string is trimmed.

  ·

  @ref{Category: Package stringproc}

Function: substring (string, start)
Function: substring (string, start, end)

  Returns the substring of string beginning at position start and ending at position end. The character at position end is not included. If end is not given, the substring contains the rest of the string. Note that the first character in string is in position 1.

      (%i1) substring("substring",4);
      (%o1)                        string
      (%i2) substring(%,4,6);
      (%o2)                          in

  ·

  @ref{Category: Package stringproc}

Function: supcase (string)
Function: supcase (string, start)
Function: supcase (string, start, end)

  Returns string except that lowercase characters from position start to end are replaced by the corresponding uppercase ones. If end is not given, all lowercase characters from start to the end of string are replaced.

      (%i1) supcase("english",1,2);
      (%o1)                        English

  ·

  @ref{Category: Package stringproc}

Function: tokens (string)
Function: tokens (string, test)

  Returns a list of tokens, which have been extracted from string. The tokens are substrings whose characters satisfy a certain test function. If test is not given, constituent is used as the default test. `{constituent, alphacharp, digitcharp, lowercasep, uppercasep, charp, characterp, alphanumericp}` is the set of test functions. (The Lisp-version of `tokens` is written by Paul Graham. ANSI Common Lisp, 1996, page 67.)

      (%i1) tokens("24 October 2005");
      (%o1)                  [24, October, 2005]
      (%i2) tokens("05-10-24",'digitcharp);
      (%o2)                     [05, 10, 24]
      (%i3) map(parse_string,%);
      (%o3)                      [5, 10, 24]

  ·

  @ref{Category: Package stringproc}

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