
DIRECTORY
Commander USING [CommandProc, Register],
IO USING [char, Error, GetChar, GetInt, int, PeekChar, PutF1, PutFR1, PutRope, Reset, SkipWhitespace, STREAM],
Process USING [Detach],
Rope USING [ROPE],
ViewerIO USING [CreateViewerStreams];

Calculate: CEDAR MONITOR   			     --(note 1.2)                                   
IMPORTS Commander, IO, Process, ViewerIO =  
BEGIN
ROPE: TYPE = Rope.ROPE;                                                     
windowCount: INT ¬ 0; -- a count of the number of calculators created.


MakeCalculator: ENTRY Commander.CommandProc = {     --(note 1.10)             
title: ROPE;
windowCount ¬ windowCount + 1;
title ¬ IO.PutFR1["Adding Machine #%g", IO.int[windowCount]];   --(note 1.11)  
TRUSTED {Process.Detach[FORK Calculate[title]];}    --(note 1.12)                 
};

Calculate: PROC[title: ROPE] = {
in, out: IO.STREAM;
[in: in, out: out] ¬ ViewerIO.CreateViewerStreams[title];    --(note 1.13)              
DO		-- Read an expression, terminated by a CR:
ENABLE IO.Error =>    			 --(note 1.14)                                                      
IF ec=SyntaxError THEN { 
IO.Reset[in];
IO.PutRope[out, "\nIncorrect input.  Please retype the expression.\n\n"];
LOOP;
}
ELSE EXIT;

answer: INT ¬ 0;		-- initialize sum to zero.
opChar: CHAR ¬ '+;		-- first integer should be added.

IO.PutRope[out, "Type one or more integers separated by + and - and terminate with CR to compute value:\n"];
DO -- Read an operator and an integer, skipping leading blanks, eg., NUL, CR, SP, etc.
number: INT ¬ IO.GetInt[in];

SELECT opChar FROM
'+ =>	answer ¬ answer + number;
'- =>	answer ¬ answer - number;
ENDCASE => {
IO.PutF1[out, "Illegal operator (%g).  Please retype the expression.\n\n", IO.char[opChar]];
EXIT;
};
IF IO.PeekChar[in]='\n THEN
GO TO NextLine;	-- the normal way out.
[]¬ IO.SkipWhitespace[in];
opChar ¬ IO.GetChar[in];

REPEAT
NextLine => {
[] ¬ IO.GetChar[in]; -- toss CR      (note 1.15)                                  
IO.PutF1[out, "\nThe answer is: %g.\n\n", IO.int[answer]];
};
ENDLOOP;
ENDLOOP;
};
Commander.Register[key: "Calculate", proc: MakeCalculator, doc: "A simple adding machine"];
END.
  4  
Calculate.mesa                                                                 
Copyright Ó 1992 by Xerox Corporation.  All rights reserved.
Last edited by: Mitchell on December 16, 1982 2:32 pm
Last edited by SChen on May 1, 1984 3:53:45 pm PDT
Last edited by Bob Hagmann on May 8, 1984 8:46:31 am PDT
Last changed by Pavel on May 5, 1989 7:15:02 pm PDT
Brian Oki, May 2, 1990 11:26 am PDT
Christian Jacobi, May 14, 1992 3:00 pm PDT
[cmd: Commander.Handle] RETURNS [result: REF ANY _ NIL, msg: ROPE _ NIL]

Puts up a calculator window.
Creates typescript window separate from CommandTool with given title.  Uses IO procedures to read an integer expression from the typescript and print its value.

Start code registers a Calculate and ReverseName command, which must be invoked for this program to do anything:
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