ExpressExampleClient.mesa
Created Thursday, June 28, 1984 10:55 am PDT
Last edited by Eric Nickell, July 13, 1984 7:45:51 pm PDT
This shows the use of the Express interface
DIRECTORY
Commander USING [CommandProc, Register],
Express USING [ClientProcList, Fcn, FreeFcn, ParseError, RopeToFcn],
IO USING [Put, real, rope],
Real USING [Fix],
Rope USING [Length, ROPE, Substr];
ExpressExampleClient:
CEDAR
MONITOR
IMPORTS C: Commander, EX: Express, IO, Real, Rope
~ {
This module, for the purpose of demonstrating Express, implements the evaluate command, which evaluates a function of i and j, both in the interval [1..5]. Also, two additional functions are implemented to show how to do this.
DoStuff:
C.CommandProc ~ {
fcn:
EX.Fcn ←
EX.RopeToFcn[expression: cmd.commandLine, symbols:
LIST["i", "j"], cProcs: clientProcList !
--NOTE: We don't use oldFcn here, 'cause we'd have to make fcn global
EX.ParseError => {
IO.Put [cmd.out, IO.rope[error.reason], IO.rope[": "]];
IO.Put [cmd.out,
IO.rope[Rope.Substr[base: cmd.commandLine, len: error.position]],
IO.rope["\000"],
IO.rope[
IF Rope.Length[cmd.commandLine]<=error.position
THEN NIL
ELSE Rope.Substr[base: cmd.commandLine, start: error.position]
]
];
GOTO DidntParse;
};
];
FOR i:
REAL ← 1, i+1.0
WHILE i<=5.0
DO
IO.Put[cmd.out, IO.rope["\t"]];
FOR j:
REAL ← 1, j+1.0
WHILE j<=5.0
DO
value: REAL ← lastValue ← fcn[i, j];
IO.Put[cmd.out, IO.real[value], IO.rope["\t"]];
ENDLOOP;
IO.Put[cmd.out, IO.rope["\n"]];
ENDLOOP;
TRUSTED {EX.FreeFcn[fcn]};
EXITS
DidntParse => RETURN
};
Some procedures to show the callback facility of Express
lastValue: REAL ← 0;
Last:
PROC
RETURNS [
REAL] ~ {
RETURN[lastValue]};
At:
PROC [addr:
REAL]
RETURNS [
REAL] ~
TRUSTED {
address: LONG POINTER TO LONG CARDINAL ← LOOPHOLE[Real.Fix[addr]];
RETURN[address^];
};
clientProcList: Express.ClientProcList ~
LIST [
[Last, "last"],
[At, "at"],
[At, "@"]
];
START UP procedure
C.Register[key: "Evaluate", doc: "Evaluate f[i,j] for 5 x 5", proc: DoStuff];
}.