#include <stdio.H>

#include <string.h>

#include <math.h>

#include <ctype.h>

float getnum(char *prmpt, int *err);

main()

{

float num;

int err;

do {

num = getnum("Input a number: ", &err);

printf("The number is %f\n", num);

} while (! err);

return 0;

}

float getnum(char *prmpt, int *err)

{

char *s, *s2, str[80], ss;

float num, d;

int n;

int sign = 1;

int decimal = 0;

*err = 0;

printf(prmpt);

gets(str);

printf("|%s|\n", str);

for(s=str; *s && *s == ' '; s++) ;

switch(*s) {

case '+':

sign = 1;

s++;

break;

case '-':

sign = -1;

s++;

break;

}

if (*s == '.') {

decimal = 1;

s++;

}

printf("|%s|\n", s);

if (! isdigit(*s)) {

*err = 1;

return 0.0;

}

for (s2=s; *s2 && isdigit(*s2); s2++) ;

ss = *s2; *s2 = 0;

n = (int)(s2 - s);

num = atoi(s);

if (decimal) {

num /= pow(10, n);

} else if (ss == '.') {

s=s2+1;

for (s2=s; *s2 && isdigit(*s2); s2++) ;

ss = *s2; *s2 = 0;

n = (int)(s2 - s);

d = atoi(s);

d /= pow(10, n);

num += d;

}

return (sign * num);

}