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According to Section 7.4 of C99:,

The header <ctype.h> declares several functions useful for classifying and mapping characters. In all cases the argument is an int, the value of which shall be representable as an unsigned char or shall equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.

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This approach is inconvenient when you need to interwork with other functions that haven't been designed with this approach in mind, forsuch example,as the string handling functions found in the standard library. \[[Kettlewell 02|AA. C References#Kettlewell 02]\].

Compliant Solution 2

This compliant solution uses an explicit cast.

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