// This was taken from a larger project I have worked on in the past. // Currently does not check for syntax errors. // Includes, sin(), cos(), tan() functions. Pow() function upcoming... using namespace std; #include #include #include #include #include enum TOKEN_TYPE { ADD, SUBSTRACT, MULT, DIVIDE, NUMBER, SYMBOL, COS, SIN, TAN, POW, COMMA, DOT, LPAREN, RPAREN, VARX, VARY, }; class Token { TOKEN_TYPE m_token; float m_fnumber; string m_symbol; int m_irank; public: Token() {} Token(TOKEN_TYPE type, float fnumber, string symbol,int irank) { m_token = type; m_fnumber = fnumber; m_symbol = symbol; m_irank = irank; } ~Token() {} int GetRank() { return m_irank; } void SetRank(int rank) { m_irank = rank; } TOKEN_TYPE GetTokenType(void) { return m_token; } float GetNumberVal(void) { return m_fnumber; } void SetNumberVal(float fnumber) { m_fnumber = fnumber; } string GetSymbol(void) { return m_symbol; } void SetSymbol(string& str) { m_symbol = str; } }; typedef list TokenList; typedef TokenList::iterator TokenIt; class Lexer { string m_formula; TokenIt m_tokit; TokenList m_toklist; public: Lexer() {} Lexer(string formula) { m_formula = formula; } ~Lexer() { for(TokenIt itor = m_toklist.begin(); itor != m_toklist.end(); ++itor) delete (*itor); } void Tokenize(void); bool IsDigit(char c) { return ((c >= 48)&&(c <= 57)); } string GetFormula(void) { return m_formula; } void SetFormula(string& formula) { m_formula = formula; } TokenList GetTokenList(void) { return m_toklist; } void AddToken(Token* tok) { m_toklist.push_back(tok); } Token GetToken(int i) { Token* tok; for(m_tokit = m_toklist.begin(); m_tokit!= m_toklist.end();) { tok = *(m_tokit); if((*m_tokit)->GetRank() == i) break; ++m_tokit; } return *tok; } }; void Lexer::Tokenize(void) { const char* buf = m_formula.c_str(); int length = strlen(buf); int i=0; int rank = 0; while(i < length) { // arithmetic symbols if(buf[i] == '+') { AddToken(new Token(ADD,0, "+",rank )); rank++; i++; } else if(buf[i] == '-') { AddToken(new Token(SUBSTRACT,0,"-",rank)); rank++; i++; } else if(buf[i] == '*') { AddToken(new Token(MULT,0, "*", rank )); rank++; i++; } else if(buf[i] == '/') { AddToken(new Token(DIVIDE,0, "/",rank )); rank++; i++; } else if(buf[i] == '(') { AddToken(new Token(LPAREN,0, "(",rank )); rank++; i++; } else if(buf[i] == ')') { AddToken(new Token(LPAREN,0, ")",rank )); rank++; i++; } else if(buf[i] == 'x') { AddToken(new Token(VARX, 0,"x",rank )); rank++; i++; } else if(buf[i] == 'y') { AddToken(new Token(VARY, 0,"y",rank )); rank++; i++; } else if(buf[i] == 'c') { string c; c += buf[i]; c += 'o'; c += 's'; AddToken(new Token(COS, 0, c, rank)); rank++; i+=3; } else if(buf[i] == 's') { string s; s += buf[i]; s += 'i'; s += 'n'; AddToken(new Token(SIN, 0, s, rank)); rank++; i+=3; } else if(buf[i] == 't') { string t; t += buf[i]; t += 'a'; t += 'n'; AddToken(new Token(TAN, 0, t, rank)); rank++; i+=3; } if(IsDigit(buf[i])||(buf[i] == '.')) { int numindex = 0; int istart = i; string number; while(IsDigit(buf[numindex+i])||(buf[numindex+i] == '.')) { number += buf[numindex+i]; numindex++; } AddToken(new Token(NUMBER, atof(number.c_str()),"",rank)); rank++; i += numindex; } } } ////////////////////////////// class Parser { Lexer* m_plexer; int m_tokenindex; Token m_tok; int m_numadds; int m_numsub; float m_varx, m_vary; public: Parser(){} Parser(Lexer* lex) { m_plexer = lex; m_tokenindex = 0; m_varx = m_vary = -1; } ~Parser(){} float GetVarX() { return m_varx; } float GetVarY() { return m_vary; } void NextToken() { m_tok = m_plexer->GetToken(m_tokenindex); m_tokenindex++; } Token LookNextToken() { Token tok = m_plexer->GetToken(m_tokenindex+1); return tok; } float Expr(void); float Term(void); float Factor(void); }; ///////////////////////////////// float Parser::Factor(void) { float fval; NextToken(); if(m_tok.GetTokenType() == NUMBER) { fval = m_tok.GetNumberVal(); } else if(m_tok.GetTokenType() == LPAREN) { fval = Expr(); NextToken(); } else if(m_tok.GetTokenType() == SUBSTRACT) { NextToken(); if(m_tok.GetTokenType() == LPAREN) { fval = -Expr(); NextToken(); } else if(m_tok.GetTokenType() == NUMBER) fval = -m_tok.GetNumberVal(); else if(m_tok.GetTokenType() == COS) { NextToken(); if(m_tok.GetTokenType() == LPAREN) { fval = -cos(Expr()); } } else if(m_tok.GetTokenType() == SIN) { NextToken(); if(m_tok.GetTokenType() == LPAREN) { fval = -sin(Expr()); } } else if(m_tok.GetTokenType() == TAN) { NextToken(); if(m_tok.GetTokenType() == LPAREN) { fval = -tan(Expr()); } } } else if(m_tok.GetTokenType() == COS) { NextToken(); if(m_tok.GetTokenType() == LPAREN) { fval = cos(Expr()); } } else if(m_tok.GetTokenType() == SIN) { NextToken(); if(m_tok.GetTokenType() == LPAREN) { fval = sin(Expr()); } } else if(m_tok.GetTokenType() == TAN) { NextToken(); if(m_tok.GetTokenType() == LPAREN) { fval = tan(Expr()); } } else if(m_tok.GetTokenType() == VARX) { fval = GetVarX(); } else if(m_tok.GetTokenType() == VARY) { fval = GetVarY(); } NextToken(); return fval; } float Parser::Term(void) { float fval; fval = Factor(); while((m_tok.GetTokenType() == MULT)||(m_tok.GetTokenType() == DIVIDE)) { if(m_tok.GetTokenType() == MULT) fval *= Factor(); else if(m_tok.GetTokenType() == DIVIDE) fval /= Factor(); } return fval; } float Parser::Expr() { float fval; fval = Term(); while((m_tok.GetTokenType() == ADD)||(m_tok.GetTokenType() == SUBSTRACT)) { if(m_tok.GetTokenType() == ADD) { fval += Term(); } else if(m_tok.GetTokenType() == SUBSTRACT) { fval -= Term(); } } return fval; } int main( ) { string expr; cin >> expr; Lexer lex(expr); Parser parser(&lex); lex.Tokenize(); float val = parser.Expr(); cout << val << "\n"; return 0; }

Calculator (includes trigonometric functions)