Re: Surprising behaviour of sqrt() on squares of integers

[Jack Brennen <jfb@brennen.net>]

I thought that the behavior was that sqrt() of a non-negative integer or 
real returns a real, and sqrtint() of a non-negative integer
returns an integer.  Both of your examples work fine with sqrtint():

? Mod(5,sqrtint(9))
Mod(2, 3)
? sqrtint(2^256)
340282366920938463463374607431768211456
? 2^128
340282366920938463463374607431768211456



On 4/23/2013 4:31 PM, Richard in Reading wrote:
> This is just a toy example but there are other real situation where it's annoying that PARI doesn't recognize when you want to take a square root of the square of an integer and return an integer.
>
> Is there some justification for this or is it worth me reporting it as a bug.
>
>   ? Mod(5,sqrt(9))
>    ***   at top-level: Mod(5,sqrt(denominat
>    ***                 ^--------------------
>    *** Mod: forbidden division t_INT % t_REAL.
>    ***   Break loop: type 'break' to go back to GP
>
> ? sqrt(2^256)
> %17 = 3.4028236692093846346337460743176821146 E38
> ? 2^128
> %18 = 340282366920938463463374607431768211456
>
> The above should return the same value in my opinion.
>
> Richard Heylen