DIRECTORY   AMTypes USING [TV],SymTab USING [Ref],Rope USING [ROPE];ExprRead: CEDAR DEFINITIONS = BEGINError: ERROR [ec: ErrorCode, msg: Rope.ROPE];ErrorCode: TYPE = {Null, 				-- never raisedCouldNotEval,							-- could not evaluate expressionNoValue,									-- expression didn't return a valueSyntax,									-- bad expression syntaxFileError,									-- could not read from fileMarkNotInTile,							-- the Mark is not in the specified cell or designPlacedTileNotInDesign,					-- the PlacedTile is not in the specified designObjectMustBeTileOrDesign				-- something else was passed};Eval: PROC [expr: Rope.ROPE, symTab: SymTab.Ref] RETURNS [AMTypes.TV];Assign: PROC [line: Rope.ROPE, symTab: SymTab.Ref];ReadFile: PROC [fileName: Rope.ROPE, symTab: SymTab.Ref];TVToRope: PROC [tv: AMTypes.TV] RETURNS[Rope.ROPE];TVToListOfRope: PROC [tv: AMTypes.TV] RETURNS[LIST OF Rope.ROPE];TVToInt: PROC [tv: AMTypes.TV] RETURNS[REF INT];TVToCardinal: PROC [tv: AMTypes.TV] RETURNS[REF CARDINAL];   -- value must be non-negativeTVToAtom: PROC [tv: AMTypes.TV] RETURNS[ATOM];END.    ø  File: ExprRead.mesa Copyright c 1984 by Xerox Corporation.  All rights reserved.Created by: Mayo, July 23, 1984 3:50:47 pm PDTLast Edited by: Mayo, July 23, 1984 6:06:17 pm PDT-- ExprRead:  Read expressions of the form 'var _ expr' or 'var ~ expr'.  If the operator is '_ then the expr is evaluated using symbols in a symbol table, or things in the global naming context.  See Interpreter.mesa for more details. If the operator is '~ then expr is simply treated as a rope which is then assigned to var.-- This module uses the slot named '&' in the passed symbol tables as a temporary placeholder. Anything that the caller places there might be destroyed.Evaluate one expression and return a TV for it's result.  Evaluate one assignment statement of the form 'var _ expr', and update var in the symbol table.  Read a file that contains one assignment statement per line.  These procedures return NIL if the operation couldn't be done, and a pointer otherwise.  They don't raise errors intentionally.Êï  ˜ šœ™Jšœ
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