The C Programming Language 2nd Edition Execise4-2 Answer

复习C语言练习，把字符串里面的数转化为浮点数。

//<<TCPG>> P4-6 by DaNmarner
#include<stdio.h>
#include<ctype.h>
double atofp (char s[])
...{
    int i,sign,expo;
    double base,sign2,power=1;
    for(i=0;isspace(s[i]);i++)
        ;
    sign=(s[i]=='-')?-1:1;
    if(s[i]=='-' || s[i]=='+') i++;
    for(base=0;isdigit(s[i]);i++)
        base=base*10+(s[i]-'0');
    if(s[i]=='.') ...{
        i++;
        for(power=1;isdigit(s[i]);i++)...{
            base=base*10+(s[i]-'0');
            power*=10;
        }
    }
    printf("%c ",s[i]);
    if(s[i]=='e' || s[i]=='E')...{
        i++;    
        printf("%c ",s[i]);
        sign2=(s[i]=='-')?0.1:10;
        printf("%f ",sign2);
        if(s[i]=='-' ||s[i]=='+') i++;
        expo=(int)atofp(s+i);
        for(;expo>0;expo--)
            power=power/sign2;
    }
    return base/power*sign;

}    

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