toupper tolower | 易学教程

问题

How to use topper and tolower in the C language? I've tried to run the program that I've made, it runs properly the problem is since I should submit it to a website to check it whether it's right or wrong, every time I submit it, it says compile error.

I made the code on macbook, using Xcode and it says on my toupper and tolower code -- implicit declaration of function 'toupper' is invalid in C99

#include <stdio.h>
#include <string.h>
int main()
{
    int input;
    scanf("%d",&input);
    int jumlahkata;

    char kalimat[100];

    for(int i=0;i<input;i++)
    {
        scanf("%s",kalimat);
        jumlahkata=strlen(kalimat);
        for(int j=0;j<jumlahkata;j++)
        {
            if(j%2==0 || j==0)
            {
                kalimat[j]=toupper(kalimat[j]);
            }
            else
            {
                kalimat[j]=tolower(kalimat[j]);
            }
        }
        printf("%s\n",kalimat);
    }

    return 0;
}

回答1:

toupper and tolower are defined in ctype.h. Simply include this file with the line #include <ctype.h>.

回答2:

You need to include header <ctype.h> .

Also int jumlahkata; should be of type size_t as you store result of strlen in it.

Or don't use it (as also pointed out by @iharob Sir ) , it unnecessary. As it is string , just check for null character as a condition in loop.

回答3:

You are mixing C with C++:

int input;
scanf("%d",&input);          // in C, following the first executable statement you may not declare variables until the next block
int jumlahkata;              // declaring the variable here is C++

char kalimat[100];           // declaring the variable here is C++

for(int i=0;i<input;i++)     // declaring the variable here is C++

来源：https://stackoverflow.com/questions/32971979/toupper-tolower

标签

tolower

toupper