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#ifndef PARSER_H
#define PARSER_H
#include <bu/list.h>
#include <bu/hash.h>
#include "token.h"
#include "number.h"
namespace Bu
{
class Stream;
};
class Lexer;
/**
*
* expr: literal
* | variable
* | expr '+' expr
* | expr '-' expr
* | expr '*' expr
* | expr '/' expr
* | '(' expr ')'
* | '-' expr
* | variable '=' expr
* ;
*
* -----
*
* expr': literal
* | variable
* | '(' expr ')'
* | '-' expr'
* ;
*
* expr: expr' '+' expr
* | expr' '-' expr
* | expr' '*' expr
* | expr' '/' expr
* | expr'
* | variable '=' expr
* ;
*/
class Parser
{
public:
Parser( Lexer &lex, Bu::Stream &rOut );
virtual ~Parser();
void parse();
Number getVariable( const Bu::String &sName );
void setVariable( const Bu::String &sName, const Number &rValue );
private:
void expr();
void exprP();
private:
void unwind();
int reqTokens( Token::Type eType );
int getPriority( Token::Type eType );
Number &deref( Token &t );
private:
Lexer &lex;
Bu::Stream &rOut;
typedef Bu::List<Token> TokenStack;
typedef Bu::Hash<Bu::String, Number> VarHash;
TokenStack tsStack;
// TokenStack tsNonTerminal;
Number nZero;
VarHash hVars;
};
#endif
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