[Haskell-cafe] clz / bsr functions on Integer

[Claude Heiland-Allen]

Hi,

On 13/11/2021 00:13, james faure wrote:
> Why is there no `countLeadingZeros` function for Integer? This seems 
> particularly strange because gmp provides 
> /mp_bitcnt_t/*mpz_scan0*/(const mpz_top, mp_bitcnt_tstarting_bit)/
Integer is not always implemented with GMP.

> More importantly, what is the recommended way to access it?
If you do have an Integer implemented with GMP (the default case with 
GHC), you can use one of

https://hackage.haskell.org/package/hgmp-0.1.2/docs/Numeric-GMP-Raw-Safe.html#v:mpz_scan0
https://hackage.haskell.org/package/hgmp-0.1.2/docs/Numeric-GMP-Raw-Unsafe.html#v:mpz_scan0

together with

https://hackage.haskell.org/package/hgmp-0.1.2/docs/Numeric-GMP-Utils.html#v:withInInteger

See the example at the top of that module page.


Claude
-- 
https://mathr.co.uk