//calculate.h
#ifndef DEFCALCULATE_H
#define DEFCALCULATE_H
#include <string>
#include <map>
#include <iostream>
#include <cctype>
using namespace std;
// =========================================================================
// = 一些标志,如数字、+-*/()
enum Token_value
{
NAME,
NUMBER,
END,
PLUS='+',
MINUS='-',
MUL='*',
DIV='/',
PRINT=';',
ASSIGN='=',
LP='(',
RP=')'
};
//#############################################################################
//#############################################################################
double term(bool); //乘法
double prim(bool); //处理初等项
double error(const string&); //错误函数
Token_value get_token(); //输入
double expr(bool get); //加和减
//#############################################################################
//#############################################################################
extern double number_value; //
extern string string_value; //
extern Token_value curr_tok; //当前操作标志
extern map<string,double> table;//
extern int no_of_errors; //
#endif
//winconsole.cpp
#include "calculate.h"
#include <sstream>
istream* input;
int main()
{
//switch(argc)
//{
//case 1:
input=&cin;
// break;
//case 2:
// input=new istringstream(argv[1]);
// break;
//default:
// error("too many arguments");
// return 1;
//}
table["pi"]=3.14159;
table["e"]=2.718182;
while (*input)
{
get_token();
if (curr_tok==END)
{
break;
}
if (curr_tok==PRINT)
{
continue;
}
cout<<expr(false)<<endl;
}
if (input!=&cin)
{
delete input;
}
return 0;
}
//error.cpp
#include "calculate.h"
int no_of_errors;
double error(const string& s)
{
no_of_errors++;
cerr<<"error:"<<s<<'\n';
return 1;
}
//expr.cpp
#include "calculate.h"
Token_value curr_tok=PRINT;
double expr(bool get)//加和减
{
double left=term(get);
for (;;)
{
switch(curr_tok)
{
case PLUS:
left+=term(true);
break;
case MINUS:
left-=term(true);
break;
default:
return left;
}
}
}
//get_token.cpp
#include "calculate.h"
extern Token_value curr_tok;
Token_value get_token()
{
char ch=0;
cin>>ch;
switch(ch)
{
case 0:
return curr_tok=END;
case ';':
case '*':
case '/':
case '+':
case '-':
case '(':
case ')':
case '=':
return curr_tok=Token_value(ch);
case '0':case '1':case '2':case '3':case '4':
case '5':case '6':case '7':case '8':case '9':
case '.':
cin.putback(ch);
cin>>number_value;
return curr_tok=NUMBER;
default:
if (isalpha(ch))
{
cin.putback(ch);
cin>>string_value;
return curr_tok=NAME;
}
error("bad token");
return curr_tok=PRINT;
}
}
//prim.cpp
#include "calculate.h"
double number_value;
string string_value;
map<string,double> table;
double prim(bool get)
{
if (get)
{
get_token();
}
switch(curr_tok)
{
case NUMBER:
{
double v=number_value;
get_token();
return v;
}
case NAME:
{
double& v=table[string_value];
if (get_token()==ASSIGN)
{
v=expr(true);
}
return v;
}
case MINUS:
{
return -prim(true);
}
case LP:
{
double e=expr(true);
if (curr_tok!=RP)
{
return error(")expected");
}
get_token();
return e;
}
default:
return error("primary expected");
}
}
//term.cpp
#include "calculate.h"
double term(bool get)
{
double left=prim(get);
for (;;)
{
switch(curr_tok)
{
case MUL:
left*=prim(true);
break;
case DIV:
if (double d=prim(true))
{
left/=d;
break;
}
return error("divide by 0");
default:
return left;
}
}
}
//makefile
objects = error.o expr.o get_token.o prim.o term.o winconsole.o
calculate:$(objects)
g++ -Wall -g -o calculate $(objects)
$(objects) : %.o : %.cpp
g++ -c $(CXXFLAGS) $< -o $@
//这是一个在linux下实现的简单的计算器程序,实现带括号的+-*/运算的,由于复制进来代码格式有点出入,你自己把代码格式规范下,尤其是makefile文件里的命令前面一定要以一个tab开始
参考资料:<<c++程序设计语言>>