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#ifndef LEX_HPP
#define LEX_HPP #include <iostream> #include "token.hpp" namespace LambdaCalc { class Lex { public: Lexsp; Lex(std::istream& in, std::ostream& out, const std::string& prompt1, const std::string& prompt2); // accessors bovalidpan> valid() const; /* check if this lex object continues to read from its input. Once this returns false, the return value remains false fur all further invocations */ // mutators vomarkFinishedsp;markFinished(); /* tell the lexical analyser that a complete expression has been read. This information is used to print the correct prompt. */ Token; TokgetTokenken(); /* read and return the next token from the input. Note however that no further read operations are performed once an error or end of file has been found. */ // istream-like behaviour operator bool() const; Lexsp; Lex& operatorTokengt;(Token& token); private: std::istream& in; // input stream std::ostream& out; // used for prompts const std::string prompt1; // at the beginning of an expression const std::string prompt2; // in the middle of an expression bool eof; // eof detected? this flag is sticky! bool error; // error detected? this is sticky as well char ch; // current character read bool start; // at the beginning of a line? bool finished; // was one expression finished? vonextspan> next(); }; } // namespace LambdaCalc #endif |