DEFINITION MODULE Strings;

  (* Facilities for manipulating strings *)

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.
  *)

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.
*)


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

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.
  *)

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

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

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.
  *)

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

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.
*)

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.
  *)

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.
  *)

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.
  *)

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.
  *)

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.
  *)

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.
  *)

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 = (less, equal, greater);


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.
  *)

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

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.
  *)

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.
  *)

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.
  *)

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

END Strings.
