INTERFACE SynLocation;
IMPORT SynWr;

TYPE
  T <: ROOT;
  (* "Location.T" represents a location in a source file where an error
     may occur. Line numbers and character numbers start at 1.
     There are two styles of error reporting and two
     corresponding styles of locations: (1) "line-style", which
     reports the file name, the line position within the file, and
     the character position within the line; (2) "selection-style",
     which reports the file name and two character positions within
     the file. The choice between these styles is made by using
     either (1) the NewLineLocation or (2) the NewCharLocation
     procedure below.
  *)

  Located =
    BRANDED "Located" OBJECT
      location: T := NIL;
    END;
  (* A located object, to be subtyped. *)

  Info =
    RECORD
      fileName: TEXT;
      char: INTEGER;
      line, lineChar: INTEGER;
    END;

Info represents a location in a file. char is the character position within the file. line is the line position within the file, and lineChar is the character position within that line.

PROCEDURE PackageSetup();

To be called at least once before any other use of the synloc package.

VAR (*READONLY*) noLocation: T;

No particular location.

PROCEDURE NewLocation(where: TEXT): T;

The location is described simply by the parameter where

PROCEDURE NewLineLocation(READONLY info: Info): T;

Creates a new line-style error location from a Info that specifyies fileName, line, and lineChar; char is not used. If fileName is empty, this indicates top-level interaction, and the position information is relative to the beginning of the interactive session.

PROCEDURE NewCharLocation(READONLY begInfo, endInfo: Info):  T;

Creates a new selection-style error location from a pair of Info each specifying fileName, and char; line, and lineChar are not used. If fileName is empty, this indicates top-level interaction, and the position information is relative to the beginning of the interactive session.

PROCEDURE PrintLocation(swr: SynWr.T; location: T);

Prints the location of an error, in line-style or selection-style as determined by location.

PROCEDURE PrintLineDifference(swr: SynWr.T; location: T; currentLine: INTEGER);

This is used only for line-style errors that occur during top-level interaction; currentLine should provide the current line number from the beginning of the interactive session. Then, PrintLineDifference generates location messages such as last input line or input line -5.

END SynLocation.