我需要在反向波兰语计算器程序中为负数添加规定，但是在测试代码时会得到此规定：
输入：
-5 7 +
输出：
error: stack empty
error: stack empty
12
这是代码中最相关的部分：
/* Getop: get next operator or numeric operand. */
int getop (char s[]) {
int i, c;
while ((s[0] = c = getch()) == ' ' || c == '\t')
;
s[1] = '\0';
if (!isdigit(c) && c!= '.' && c!= '-')
return c; /* Not a number */
i = 0;
if (c == '-') {
if(isdigit(s[i]) || s[i] == '.') {
c = s[i]; /* Copy c to s[i], first character of the
number */
++i;
}
else {
return c;
}
}
if (isdigit(c)) /* collect integer part */
while (isdigit(s[++i] = c = getch()))
;
if (c == '.')
while (isdigit(s[++i] = c = getch()))
;
s[i] = '\0';
if (c != EOF)
ungetch(c);
return NUMBER;
}
我不知道自己在做什么错，因此将不胜感激。
由乡亲建议编辑：
#include <stdio.h>
#include <stdlib.h> /* for atof() */
#include <ctype.h>
#include <math.h>
#define MAXOP 100 /* max size of operand or operator */
#define NUMBER '0' /* signal that a number was found */
#define MAXVAL 100 /* maximum depth of val stack */
#define BUFSIZE 100
int sp = 0; /* next free stack position */
double val[MAXVAL]; /* value stack */
int getop(char s[]);
void push(double);
double pop(void);
int pop_int(void);
int getch (void);
void ungetch(int);
/* reverse Polish calculator */
int main()
{
int type;
double op2;
char s[MAXOP];
while ((type = getop(s)) != EOF) {
switch (type) {
case NUMBER:
push (atof(s));
break;
case '+':
push( pop() + pop() );
break;
case '*':
push(pop() * pop());
break;
case '-':
op2 = pop(); /* Addition on the real numbers is commutative because for any real numbers s,t, it is true that s+t=t+s.
Addition and multiplication are commutative operations but subtraction and division are not. */
push(pop() - op2);
break;
case '/':
op2 = pop();
if (op2 != 0.0)
push(pop() / op2);
else
printf("error: zero divisor\n");
break;
case '%':
op2 = pop();
push(fmod(pop(), op2));
break;
case '\n':
printf("\t%.8g\n" , pop());
break;
default:
printf("error: unknown command %s\n", s);
break;
}
}
return 0;
}
/* push : push f onto value stack */
void push(double f)
{
if (sp < MAXVAL)
val[sp++] = f;
else
printf("error: stack full, can`t push %g\n", f);
}
/* pop: pop and return top value from stack */
double pop(void)
{
if (sp > 0)
return val[--sp];
else {
printf("error: stack empty\n");
return 0.0;
}
}
最佳答案
尝试此为getop：
int getop(char s[]) {
int i, c;
while ((s[0] = c = getch()) == ' ' || c == '\t')
;
s[1] = '\0';
if (!isdigit(c) && c != '.' && c != '-')
return c; /* Not a number */
i = 0;
if (c == '-')
{
while (isdigit(s[++i] = c = getch()))
}
if (isdigit(c)) /* collect integer part */
while (isdigit(s[++i] = c = getch()))
;
if (c == '.')
while (isdigit(s[++i] = c = getch()))
;
s[i] = '\0';
if (c != EOF)
ungetch(c);
return NUMBER;
}
关于c - Getop函数负数，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/31940217/