Re: [Caml-list] Num library

[Jean-Christophe Filliatre <filliatr@lri.fr>]

Alain Frisch writes:
 > 
 > I'm considering using the Num library (from the standard distribution) for
 > implementing numbers in an interpreter. Questions:
 > 
 > - How does the library compare with other large/rational numbers
 >   implementations ?

I'm not going to comment on the efficiency of Num.

But, for  having tried  to use  it in a  serious software  and finally
replaced  it by  mlgmp, I  can mention  one true  weakness of  the Num
library: there is  no unicity of representation (e.g. 1  can be Int 1,
but  also Ratio  1/1, etc.)  and  consequently you  cannot use  caml's
comparison and hash functions over it.

Of course, you  can use compare_num (hash_num is  lacking, though) but
when  nums are  involved  within  huge datatypes,  you  have to  write
structural comparison  and hash functions  for these types. This  is a
pain, really.

-- 
Jean-Christophe

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