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* Some more explanations

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git-svn-id: trunk@12011 -
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michael 2008-11-01 22:28:04 +00:00
parent f3dccf9e7d
commit c85ce877fb
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38
packages/fcl-base/examples/fpexprpars.txt
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@ -99,4 +99,42 @@ match. If no match is found, Def will be returned. From this it follows that
2) The types of Tag, label1, label2 must be the same;
3) The types of Def, Value1, Value2 must be the same;
As soon as the expression is set, it is compiled and checked. Thus
FP.Expression:='1*2';
will work.
On the other hand
FP.Expression:=' 1 * ''a string''';
will result in an exception because 1 and ''a string'' do not have the same
type.
Getting the result is quite simple
FP.Expression:='1*2';
Writeln(FP.AsInteger);
This will raise an exception if the type of the result is not integer.
In case the expression result type is unknown, it can be examined using
the ResultType function, as in :
FP.Expression:='Some user-provided expression';
Case FP.ResultType of
rtString : Writeln(FP.Evaluate.ResString);
rtInteger : Writeln(FP.Evaluate.ResInteger);
rtFloat : Writeln(FP.Evaluate.ResFloat);
rtBoolean : Writeln(FP.Evaluate.ResBoolean);
rtDateTime : Writeln(FormatDateTime('cccc',FP.Evaluate.ResDateTime));
end;
Which is equivalent to
FP.Expression:='Some user-provided expression';
Case FP.ResultType of
rtString : Writeln(FP.AsString);
rtInteger : Writeln(FP.AsInteger);
rtFloat : Writeln(FP.AsFloat);
rtBoolean : Writeln(FP.AsBoolean);
rtDateTime : Writeln(FormatDateTime('cccc',FP.AsDateTime));
end;