// Meta-program to calculate number of digits in (unsigned) 'N'. template <unsigned long long N, unsigned base=10> struct numberlength { enum { value = ( 1<=N && N<base ? 1 : 1+numberlength<N/base, base>::value ) }; }; template <unsigned base> struct numberlength<0, base> { enum { value = 1 }; }; { assert( (1 == numberlength<0,10>::value) ); } assert( (1 == numberlength<1,10>::value) ); assert( (1 == numberlength<5,10>::value) ); assert( (1 == numberlength<9,10>::value) ); assert( (4 == numberlength<1000,10>::value) ); assert( (4 == numberlength<5000,10>::value) ); assert( (4 == numberlength<9999,10>::value) ); 

// Meta-program to calculate number of digits in (unsigned) 'N'. template <unsigned long long N, unsigned base=10> struct numberlength { // http://stackoverflow.com/questions/1489830/ enum { value = ( 1<=N && N<base ? 1 : 1+numberlength<N/base, base>::value ) }; }; template <unsigned base> struct numberlength<0, base> { enum { value = 1 }; }; { assert( (1 == numberlength<0,10>::value) ); } assert( (1 == numberlength<1,10>::value) ); assert( (1 == numberlength<5,10>::value) ); assert( (1 == numberlength<9,10>::value) ); assert( (4 == numberlength<1000,10>::value) ); assert( (4 == numberlength<5000,10>::value) ); assert( (4 == numberlength<9999,10>::value) );