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 stringVar: 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.

