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May 31, 2017 08:13
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Alternative way to check whether an ascii character is a letter or not.
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| #include <stdio.h> | |
| #define TOLOWER(c) ((c) | 0x20) | |
| #define ISLETTER(c) ((unsigned char)(TOLOWER(c) - 'a') < 26) | |
| int main(int argc, char *argv[]) | |
| { | |
| if (argc != 2 || argv[1][1] != '\0') { | |
| puts("Usage: isletter <character>"); | |
| return 1; | |
| } | |
| if (ISLETTER(argv[1][0])) puts("It is a letter indeed."); | |
| else puts("Not a letter."); | |
| return 0; | |
| } |
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