.. _gm2-libs-iso-strings:

gm2-libs-iso/Strings
^^^^^^^^^^^^^^^^^^^^

.. code-block:: modula2

  DEFINITION MODULE Strings;

    (* Facilities for manipulating strings *)

  TYPE
  String1 (type)
    String1 = ARRAY [0..0] OF CHAR;
      (* String1 is provided for constructing a value of a single-character string type from a
         single character value in order to pass CHAR values to ARRAY OF CHAR parameters.
      *)

  Length
  PROCEDURE Length (stringVal: ARRAY OF CHAR): CARDINAL;
    (* Returns the length of stringVal (the same value as would be returned by the
       pervasive function LENGTH).
    *)

  (* The following seven procedures construct a string value, and attempt to assign it to a
     variable parameter.  They all have the property that if the length of the constructed string
     value exceeds the capacity of the variable parameter, a truncated value is assigned, while
     if the length of the constructed string value is less than the capacity of the variable
     parameter, a string terminator is appended before assignment is performed.
  *)

  Assign
  PROCEDURE Assign (source: ARRAY OF CHAR; VAR destination: ARRAY OF CHAR);
    (* Copies source to destination *)

  Extract
  PROCEDURE Extract (source: ARRAY OF CHAR; startIndex, numberToExtract: CARDINAL;
                     VAR destination: ARRAY OF CHAR);
    (* Copies at most numberToExtract characters from source to destination, starting at position
       startIndex in source.
    *)

  Delete
  PROCEDURE Delete (VAR stringVar: ARRAY OF CHAR; startIndex, numberToDelete:
  CARDINAL);
    (* Deletes at most numberToDelete characters from stringVar, starting at position
       startIndex.
    *)

  Insert
  PROCEDURE Insert (source: ARRAY OF CHAR; startIndex: CARDINAL;
                    VAR destination: ARRAY OF CHAR);
    (* Inserts source into destination at position startIndex *)

  Replace
  PROCEDURE Replace (source: ARRAY OF CHAR; startIndex: CARDINAL;
                     VAR destination: ARRAY OF CHAR);
    (* Copies source into destination, starting at position startIndex. Copying stops when
       all of source has been copied, or when the last character of the string value in
       destination has been replaced.
    *)

  Append
  PROCEDURE Append (source: ARRAY OF CHAR; VAR destination: ARRAY OF CHAR);
    (* Appends source to destination. *)

  Concat
  PROCEDURE Concat (source1, source2: ARRAY OF CHAR; VAR destination: ARRAY OF CHAR);
    (* Concatenates source2 onto source1 and copies the result into destination. *)

  (* The following predicates provide for pre-testing of the operation-completion
     conditions for the procedures above.
  *)

  CanAssignAll
  PROCEDURE CanAssignAll (sourceLength: CARDINAL; VAR destination: ARRAY OF CHAR): BOOLEAN;
    (* Returns TRUE if a number of characters, indicated by sourceLength, will fit into
       destination; otherwise returns FALSE.
    *)

  CanExtractAll
  PROCEDURE CanExtractAll (sourceLength, startIndex, numberToExtract: CARDINAL;
                           VAR destination: ARRAY OF CHAR): BOOLEAN;
    (* Returns TRUE if there are numberToExtract characters starting at startIndex and
       within the sourceLength of some string, and if the capacity of destination is
       sufficient to hold numberToExtract characters; otherwise returns FALSE.
    *)

  CanDeleteAll
  PROCEDURE CanDeleteAll (stringLength, startIndex, numberToDelete: CARDINAL): BOOLEAN;
    (* Returns TRUE if there are numberToDelete characters starting at startIndex and
       within the stringLength of some string; otherwise returns FALSE.
    *)

  CanInsertAll
  PROCEDURE CanInsertAll (sourceLength, startIndex: CARDINAL;
                          VAR destination: ARRAY OF CHAR): BOOLEAN;
    (* Returns TRUE if there is room for the insertion of sourceLength characters from
       some string into destination starting at startIndex; otherwise returns FALSE.
    *)

  CanReplaceAll
  PROCEDURE CanReplaceAll (sourceLength, startIndex: CARDINAL;
                           VAR destination: ARRAY OF CHAR): BOOLEAN;
    (* Returns TRUE if there is room for the replacement of sourceLength characters in
       destination starting at startIndex; otherwise returns FALSE.
    *)

  CanAppendAll
  PROCEDURE CanAppendAll (sourceLength: CARDINAL; VAR destination: ARRAY OF CHAR): BOOLEAN;
    (* Returns TRUE if there is sufficient room in destination to append a string of
       length sourceLength to the string in destination; otherwise returns FALSE.
    *)

  CanConcatAll
  PROCEDURE CanConcatAll (source1Length, source2Length: CARDINAL;
                          VAR destination: ARRAY OF CHAR): BOOLEAN;
    (* Returns TRUE if there is sufficient room in destination for a two strings of
       lengths source1Length and source2Length; otherwise returns FALSE.
    *)

  (* The following type and procedures provide for the comparison of string values, and for the
     location of substrings within strings.
  *)

  TYPE
  CompareResults (type)
    CompareResults = (less, equal, greater);

  Compare
  PROCEDURE Compare (stringVal1, stringVal2: ARRAY OF CHAR): CompareResults;
    (* Returns less, equal, or greater, according as stringVal1 is lexically less than,
       equal to, or greater than stringVal2.
    *)

  Equal
  PROCEDURE Equal (stringVal1, stringVal2: ARRAY OF CHAR): BOOLEAN;
    (* Returns Strings.Compare(stringVal1, stringVal2) = Strings.equal *)

  FindNext
  PROCEDURE FindNext (pattern, stringToSearch: ARRAY OF CHAR; startIndex: CARDINAL;
                      VAR patternFound: BOOLEAN; VAR posOfPattern: CARDINAL);
    (* Looks forward for next occurrence of pattern in stringToSearch, starting the search at
       position startIndex. If startIndex < LENGTH(stringToSearch) and pattern is found,
       patternFound is returned as TRUE, and posOfPattern contains the start position in
       stringToSearch of pattern. Otherwise patternFound is returned as FALSE, and posOfPattern
       is unchanged.
    *)

  FindPrev
  PROCEDURE FindPrev (pattern, stringToSearch: ARRAY OF CHAR; startIndex: CARDINAL;
                      VAR patternFound: BOOLEAN; VAR posOfPattern: CARDINAL);
    (* Looks backward for the previous occurrence of pattern in stringToSearch and returns the
       position of the first character of the pattern if found. The search for the pattern
       begins at startIndex. If pattern is found, patternFound is returned as TRUE, and
       posOfPattern contains the start position in stringToSearch of pattern in the range
       [0..startIndex]. Otherwise patternFound is returned as FALSE, and posOfPattern is unchanged.
    *)

  FindDiff
  PROCEDURE FindDiff (stringVal1, stringVal2: ARRAY OF CHAR;
                      VAR differenceFound: BOOLEAN; VAR posOfDifference: CARDINAL);
    (* Compares the string values in stringVal1 and stringVal2 for differences. If they
       are equal, differenceFound is returned as FALSE, and TRUE otherwise. If
       differenceFound is TRUE, posOfDifference is set to the position of the first
       difference; otherwise posOfDifference is unchanged.
    *)

  Capitalize
  PROCEDURE Capitalize (VAR stringVar: ARRAY OF CHAR);
    (* Applies the function CAP to each character of the string value in stringVar. *)

  END Strings.