test4_.c

利用递归实现的计算器编译器

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#define MAX 100

static int stack[MAX];
int sp = 0;
int sp_copy = 0;
char buf[20];
int chack = 0;

int pop(void);
void push(int);
int get_number(void);
int volatile operate(void);
void p (void);

int main()
{
	int k = 0;
	char c;
	printf("please input\n");
	c= getchar();
	for(;c != '\n';)
	{
		if(k > 20)
		{
			printf("you in put is too lang\n");
			return 0;
		}
		if(isspace(buf[k]))
			;
		else
		{
		buf[k] = c;
		k++;
		}		
		c = getchar();
	}
	buf[k] = '\n';
	printf("buf%s\n",buf);
	printf("res = %d\n",operate());

}

 int volatile operate()
{
	int num;
	push (sp_copy);	
	sp_copy = sp;

	for(;;)
	{
		if(isdigit(buf[chack]))
		{
			num = get_number();
			push(num);
		}
		switch(buf[chack])
		{
			case'+':
			{
lab:				chack++;
                                if(buf[chack] == '(')
                                {
                                        chack++;
                                        num = 0;
                                        num = operate();
                                        push(num);
                                        break;
				}
				else
				{
					num = 0;
					num = get_number();
					push(num);
					break;	
				}
			}
			case'-':
			{
				if(buf[chack+1] == '-')
				{	
					chack++;
					goto lab;
				}
				chack++;
                                if(buf[chack] == '(')
                                {
                                        chack++;
                                        num = 0;
                                        num = operate();
                                        num = num * (-1);
                                        push(num);
                                        break;
				}
				else
				{
					num = 0;
					num = get_number();
					num = num * (-1);
					push(num);
					break;
				}
			}
			case'*':
			{
				chack++;
				if(buf[chack] == '(')
				{
					chack++;
					num = 0;
					num = operate();
					num = num * pop();
					push(num);
					break;
				}
				else
				{
				        num = 0;
                                        num = get_number();
                                        num = num * pop();
                                        push(num);
                                        break;
				}
			}	
			case'/':
			{
				chack++;
				if(buf[chack] == '(')
				{
					chack++;
					num = 0;
					num = operate();
					num = pop() / num;
					push(num);
					break;
				}
				else
				{
				        num = 0;
                                        num = get_number();
                                        num = pop() / num;
                                        push(num);
                                        break;
				}
			}
			case'(':
			{
				num = 0;
				chack++;
				num = operate();
				push(num);
				break;				
			}			
			case')':
			{
				chack++;
				num = 0;
				for(;!(sp == (sp_copy));)
				{	
					
					num = num + pop();
//					printf("num=%d\n",num);
					
				}
				sp_copy = pop();
				return num;	
			}
			case'\n':
			{
				num = 0;
				for(;!(sp == (sp_copy));)
				{	
					
					num = num + pop();
//					printf("num=%d\n",num);
					
				}
				sp_copy = pop();
				return num;
			}
			default:
			{
			printf("input error\n");
			return 0;
			}
		}
		
	}										
}



int get_number(void)
{
	int temp = 0;
	int i;
	for(i=0;isdigit(buf[chack]);chack++)
	{
		temp = temp*10+(buf[chack] - '0');	
	}	
//	printf("get=%d\n",temp);		
	return temp;
}


void push(int f)
{
	if (sp < MAX)
		{
		stack[sp++] = f;
		printf("push %d  sp== %d  ",f,sp);
		p();
		}
	else
		;
	//	printf("stack full\n");
}


int pop(void)
{
	if (sp >= 0)
		{
		sp--;
		printf("pop %d   sp== %d  ",stack[sp],sp);
		p();
		return stack[sp];
		}
	else
	{
//		printf("stack empty\n");
		return 0;
	}
}




void p(void)
{
	int i;
	printf(" : ");
	for(i = 0;i < sp;i++)
		printf("%d   ",stack[i]);
	printf("\n");

}