// This program takes an arithmetic expression that includes the *, /, +, -, (,) operators and calculates the result using recursive descent. Currently only supports integers as operands. // Examples : 2*3+5=11 // (2+3)*5=25 // You can put spaces between the chars it will work as well. // Note: don't try to use the SoloLearn keyboard to enter operators cause it won't let you. Feel free to comment and report bugs. #include #include #include #include using namespace std; #define MAXTOKENS 256 enum tokentype { NUM, PLUS, MINUS, MULT, DIV, PARENLEFT, PARENRIGHT, }; struct Token { tokentype type; char c; int num; }; class Lexer { string expr; Token tokens[MAXTOKENS]; int numtoks; bool lexerror; public: Lexer() { } Lexer(string& expr) { this->expr=expr; lexerror=false; } Token* getTokens() { return tokens; } int numTokens() { return numtoks; } bool error(){return lexerror;} void scan() { int numtokens=0; int i=0; string s="0123456789"; string c="0123456789*/()+- "; while(ilex=lex; numtokens=lex.numTokens(); tokpos=0; } void displayToken(int i) { if(lex.getTokens()[i].type==NUM) cout<

Expression Evaluator