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c++ccharactertoupper

Why is the alphabet split into multiple ranges in this C code?

In a custom library I saw an implementation:

inline int is_upper_alpha(char chValue)
{
    if (((chValue >= 'A') && (chValue <= 'I')) ||
        ((chValue >= 'J') && (chValue <= 'R')) ||
        ((chValue >= 'S') && (chValue <= 'Z')))
        return 1;
    return 0;
}

Is that an Easter egg or what are the advantages vs standard C/C++ method?

inline int is_upper_alpha(char chValue)
{
    return ((chValue >= 'A') && (chValue <= 'Z'));
}
Solution

  • The author of this code presumably had to support EBCDIC at some point, where the numeric values of the letters are non-contiguous (gaps exist between I, J and R, S, as you may have guessed).

    It is worth noting that the C and C++ standards only guarantee that the characters 0 to 9 have contiguous numeric values for precisely this reason, so neither of these methods is strictly standard-conforming.