eval_expr.h

来自「斯坦福Energy211/CME211课《c++编程——地球科学科学家和工程师》」· C头文件 代码 · 共 37 行

// This header file includes declarations that are needed
// in more than one source file

#include <iostream>
#include <sstream>
#include <stack>

// These numeric codes identify the various types of tokens
// that can appear in an expression, which are numbers,
// arithmetic operators, and parentheses.  
#define TOK_NUM		100
#define TOK_ADD		101
#define TOK_SUB		102
#define TOK_MUL		103
#define TOK_DIV		104
#define TOK_NEG		105
#define TOK_LPAR	106
#define TOK_RPAR	107
// These tokens are included to easily detect and process
// the end of input
#define TOK_ERR		200
#define TOK_EOF		201
#define TOK_EOL		202

using namespace std;

// A stack of doubles is used to evaluate an expression.
// Operands are pushed onto the stack.  When an operation
// is performed, its operands are popped off of the stack,
// the operation is performed on them, and the result is
// pushed back onto the stack
typedef stack<double> value_stack;

// Main scanning and parsing functions
int nexttoken( string& tok_str );
int Expr( value_stack& s, int token, string& tok_str );