C - 打印函数返回的字符

Question

更新:最后的 if 语句 if(lettergrade <= 'A' && lettergrade >= 'F')错误，因为 F (70) 的 ascii 值大于 A (65)。

我正在尝试打印 C 中函数返回的字符。

我的函数 allocateletter 被赋予一个 float ，并返回一个字符。

当我按原样运行程序时:

skirchbaum:~/workspace/HMWK/HMWK4 $ ./assignletter 
Enter pointsgrade
100
Pointsgrade: 100.00 Lettergrade: 

没有打印任何字母等级(我尝试过多种情况 - 100.1、1 等)

我做错了什么？

代码:

/* Input: a grade as points
   Functionality: converts point grade into letter grade
   Output: a char representing the letter grade, or -1 if error

   LETTER GRADE BREAKDOWN:
   A = 100 - 91
   B = 90 - 81
   C = 80 - 71
   D = 70 - 61
   F = 60 and below
*/


#include <stdio.h>
#include <stdlib.h>
#define DEBUG 1

char assignletter(float pointsgrade);

char lettergrade;
float pointsgrade;

int main(){
    //Input a pointsgrade for debugging
    #ifdef DEBUG
    printf("Enter pointsgrade\n");
    scanf("%f", &pointsgrade);
    lettergrade = assignletter(pointsgrade);
    printf("Pointsgrade: %.2f Lettergrade: %c\n", pointsgrade, lettergrade);
    #endif
}

char assignletter(float pointsgrade){

    char lettergrade;

    //Grade A
    if(pointsgrade <= 100 && pointsgrade >= 91){
        lettergrade = 'A';
    }

    //Grade B
    if(pointsgrade <= 90 && pointsgrade >= 81){
        lettergrade = 'B';
    }

    //Grade C
    if(pointsgrade <= 80 && pointsgrade >= 71){
        lettergrade = 'C';
    }

    //Grade D
    if(pointsgrade <= 70 && pointsgrade >= 61){
        lettergrade = 'D';
    }

    //Grade F
    if(pointsgrade <= 60){
        lettergrade = 'F';
    }

    //Return letter grade or -1 if error
    if(lettergrade <= 'A' && lettergrade >= 'F'){
        return lettergrade;
    }
    else{
        return -1;
    }
}

Answer 1

条件格式不正确，ASCII 中的“F”为 70 'A' 是 65 所以

if (lettergrade <= 'A' && lettergrade >= 'F') {
    return lettergrade;
}

不会评估为 true，因为字母等级 ('A') 小于 70 ('F') 并且不大于它

你宁愿这样做

if (lettergrade >= 'A' && lettergrade <= 'F') {
    return lettergrade;
}

通过翻转大于和小于符号