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101 lines
2.9 KiB
ObjectPascal
101 lines
2.9 KiB
ObjectPascal
{
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$ id: $
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Copyright (c) 2000 by Marco van de Voort (marco@freepascal.org)
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member of the Free Pascal development team
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See the file COPYING.FPC, included in this distribution,
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for details about the copyright. (LGPL)
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Most basic test for TEvaluator class.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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**********************************************************************
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}
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program EvalTest;
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{$AppType Console}
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Uses Classes,Symbolic, SysUtils;
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VAR Expr : TExpression;
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SymVars : TStringList;
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I : Longint;
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VarName : TStringList;
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Eval : TEvaluator;
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Vars : Array[0..1] OF ArbFloat;
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begin
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{Lets create in a nice equation. Totally nonsense. Don't try to
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make sense of it}
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Expr:=TExpression.Create('pi*sin(x-x0)+x^(t-1)+exp(x*t)+5');
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Writeln('Expression after parsing :',Expr.InfixExpr);
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{Hmm. But the user could have typed that in. Let's check if he used
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symbolic values}
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SymVars:=Expr.SymbolicValueNames;
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If SymVars.Count>0 Then
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For I:=0 TO SymVars.Count-1 DO
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Writeln(I:5,' ',Symvars[I]);
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{Assume the user selected X and T from above stringlist as our variables}
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VarName:=TStringList.Create;
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VarName.Add('X');
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VarName.Add('T');
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{Create the Evaluator Object}
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Eval:=TEvaluator.Create(VarName,Expr);
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{My HP48g provided this value for PI:}
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IF Symvars.IndexOf('PI')<>-1 THEN {If PI exists, then assume it is the
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circle radius vs diameter ratio}
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Eval.SetConstant('PI',3.14159265359);
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IF Symvars.IndexOf('X0')<>-1 THEN {Set X0 to Douglas' number}
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Eval.SetConstant('X0',42);
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{All this above looks slow isn't? It probably even is. Unit symbolic has
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evaluations as plus, not as target. The evaluation is built for
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fast repeated evaluations, not just one.
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However the Evaluate method is hopefully reasonably fast.
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Under FPC TEvaluator.Evaluate is about 600-700 assembler instructions,
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without operation on pointer trees and without recursion.
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If your compiler (and hopefully FPC too) can inline the math unit functions,
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the speed gain could be dramatic.}
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Writeln('Stackdepth needed for evaluation: ',eval.EvalDepth);
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FOR I:=1 TO 50 DO
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begin
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Vars[0]:=1/I *1.1;
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Vars[1]:=1/I*2;
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Writeln(VarName.Strings[0] + '=' + FloatToStrF(Vars[0], ffFixed, 4, 4) + ' ' +
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VarName.Strings[1] + '=' + FloatToStrF(Vars[1], ffFixed, 4, 4) + ' = ' +
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FloatToStrF(Eval.Evaluate(Vars), ffFixed, 4, 4));
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end;
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Eval.Free;
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Expr.Free;
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SymVars.Free;
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// VarName.Free; {Is freed by TEvaluator.Destroy. Should TEvaluator copy it?}
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Readln;
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end.
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{
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$Log$
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Revision 1.1 2002/12/15 21:01:22 marco
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Initial revision
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}
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