Re: strtoul etc.

[Branko Cibej <branko.cibej@hermes.si>]

Ryszard Kabatek wrote:

> Below a sample of the simplest (base == 10) conversion
> from a string to an integer.

Are you quite sure it's the simplest?

     template <typename Iter, typename Int>
     bool AtoN10 (Iter first, Iter last, Int& value)
     {
       assert (numeric_limits<Int>::is_integer);

       typedef char_traits<Iter::value_type> Traits;

       Int const max_val = numeric_limits<Int>::max();
       Int const base    = 10;
       Int const cutoff  = max_val / base;
       Int const cutlim  = max_val % base;

       Traits::char_type const nought = Traits::to_char_type ('0');

       value = 0;
       Traits::char_type c;
       int sign = 1;

       // Check the sign
       if (first != last && !isdigit(c = *first)) {
         if (c == Traits::to_char_type ('-')) {
           if (!numeric_limits<Int>::is_signed)
             return false;
           sign = -1;
           ++first;
         }
         else if (c == Traits::to_char_type ('+'))
           ++first;
         else
           return false;
       }
       if (first == last)
         return false;

       // Skip leading zeroes
       while (first != last && isdigit (c = *first) && c == nought)
         ++first;

       while (first != last && isdigit (c = *first)) {
         Int n = c - nought;
         if (value > cutoff || (value == cutoff && n > cutlim))
           return false;
         value *= base;
         value += n;
         ++first;
       }

       value *= sign;
       if (first != last)
         return false;

       return true;
     }

> I think we should decide if we want to go this way.
> I suppose it depends on the answer to the question:
>
> Does somebody want to implement the necessary functions?

No :-)

--
Branko Čibej                 <branko.cibej@hermes.si>
HERMES SoftLab, Litijska 51, 1000 Ljubljana, Slovenia
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