Why does “dtoa.c” contain so much code?

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dtoa.c contains two main functions: dtoa(), which converts a double to string, and strtod(), which converts a string to a double. It also contains a lot of support functions, most of which are for its own implementation of arbitrary-precision arithmetic. dtoa.c’s claim to fame is getting these conversions right, and that can only be done, in general, with arbitrary-precision arithmetic. It also has code to round conversions correctly in four different rounding modes.

Your code only tries to implement the equivalent of dtoa(), and since it uses floating-point to do its conversions, will not always get them right. (Update: see my article http://www.exploringbinary.com/quick-and-dirty-floating-point-to-decimal-conversion/ for details.)

(I’ve written a lot about this on my blog, http://www.exploringbinary.com/ . Six of my last seven articles have been about strtod() conversions alone. Read through them to see how complicated it is to do correctly rounded conversions.)

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