75 lines
2.3 KiB
C
75 lines
2.3 KiB
C
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//===== Copyright <20> 1996-2006, Valve Corporation, All rights reserved. ======//
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//
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// Purpose: ExprSimplifier builds a binary tree from an infix expression (in the
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// form of a character array).
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//
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//===========================================================================//
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#ifndef EXPREVALUATOR_H
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#define EXPREVALUATOR_H
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#if defined( _WIN32 )
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#pragma once
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#endif
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static const char OR_OP = '|';
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static const char AND_OP = '&';
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static const char NOT_OP = '!';
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#define MAX_IDENTIFIER_LEN 128
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enum Kind {CONDITIONAL, NOT, LITERAL};
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struct ExprNode
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{
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ExprNode *left; // left sub-expression
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ExprNode *right; // right sub-expression
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Kind kind; // kind of node this is
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union
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{
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char cond; // the conditional
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bool value; // the value
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} data;
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};
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typedef ExprNode *ExprTree;
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// callback to evaluate a $<symbol> during evaluation, return true or false
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typedef bool (*GetSymbolProc_t)( const char *pKey );
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typedef void (*SyntaxErrorProc_t)( const char *pReason );
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class CExpressionEvaluator
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{
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public:
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CExpressionEvaluator();
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~CExpressionEvaluator();
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bool Evaluate( bool &result, const char *pInfixExpression, GetSymbolProc_t pGetSymbolProc = 0, SyntaxErrorProc_t pSyntaxErrorProc = 0 );
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private:
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CExpressionEvaluator( CExpressionEvaluator& ); // prevent copy constructor being used
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char GetNextToken( void );
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void FreeNode( ExprNode *pNode );
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ExprNode *AllocateNode( void );
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void FreeTree( ExprTree &node );
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bool IsConditional( bool &bCondition, const char token );
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bool IsNotOp( const char token );
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bool IsIdentifierOrConstant( const char token );
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bool MakeExprNode( ExprTree &tree, char token, Kind kind, ExprTree left, ExprTree right );
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bool MakeFactor( ExprTree &tree );
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bool MakeTerm( ExprTree &tree );
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bool MakeExpression( ExprTree &tree );
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bool BuildExpression( void );
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bool SimplifyNode( ExprTree &node );
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ExprTree m_ExprTree; // Tree representation of the expression
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char m_CurToken; // Current token read from the input expression
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const char *m_pExpression; // Array of the expression characters
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int m_CurPosition; // Current position in the input expression
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char m_Identifier[MAX_IDENTIFIER_LEN]; // Stores the identifier string
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GetSymbolProc_t m_pGetSymbolProc;
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SyntaxErrorProc_t m_pSyntaxErrorProc;
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bool m_bSetup;
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};
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#endif
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