JCL Help:TExprSym
JCL Help: TExprSym Class
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TExprSym
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TExprAbstractFuncSym
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TExprConst32Sym
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TExprConst64Sym
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TExprConst80Sym
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TExprConstSym
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TExprVar32Sym
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TExprVar64Sym
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TExprVar80Sym
Summary
Represents a symbol that may be found in an input stream.
Pascal
public TExprSym = class(TObject);
Description
An instance of this class is responsible for turning input lexemes (from the lexer) into either a concrete result (Evaluate) or expression nodes (Compile).
Because this class has state (properties like Lexer, EvalParser, CompileParser, NodeFactory), a symbol should never be used by two threads simultaneously. This design decision was taken to maximize ease of creating new symbols.
It is, however, safe to implement recursive symbols (i.e. a symbol that calls itself, even though it might be through another evaluator with different Lexer etc.) because the state is saved before Evaluate or Compile is called, and restored afterwards.
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Unit
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Barry Kelly
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