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`iswdigit'--decimal digit wide-character test

     #include <wctype.h>
     int iswdigit(wint_t C);
`iswdigit' is a function which classifies wide-character values that
are decimal digits.
`iswdigit' returns non-zero if C is a decimal digit wide-character.
`iswdigit' is C99.
   No supporting OS subroutines are required.