### Re: Math::BigInt and bigint with non-integers

tor. 19. aug. 2021 kl. 16:40 skrev Dan Book : > > > Truncation to integer seems the most useful and expected behavior to me. Not sure if the "overloading of constants" case should be affected, would people depend on it staying unmodified? I agree on truncation to integer. This is consistent with how Perl treats non-integers in integer context. E.g., $a[0.9] returns $a[0], not $a[1]. I know nothing about the context in which people use "use Math::BigInt=:constant" or "use bigint". I would suspect that these are only used when people are using integers only. As soon as a non-integer interacts with the overloaded literal integers, it is converted to an integer (with "bignum") $ perl -Mbigint -wle 'print 2 + 3.16' 5 or a NaN (with "Math::BigInt") $ perl -MMath::BigInt=:constant -wle 'print 2 + 3.16' NaN It seems most sensible to me that both cases should return 5. It would be nice if Math::BigInt->new("3.16") also returned 3, not NaN as now. However, people might rely on this behaviour. I might search through the CPAN modules and see if I can find any use cases. Peter

### Re: Math::BigInt and bigint with non-integers

Consistency is good. A case could be made for either truncating to integer, or rounding to integer. I'm inclined toward round - since int() is a builtin (round isn't), which makes it easy to get the truncate behavior. And one is more likely to get a mathematically sensible result. On the other hand, changing long-standing behavior may wake the dragons. I don't like bug compatibility switches, but in this case a "use Math::Biging qw/roundtoint/" (or whatever you choose) might be worth considering. Unless you're up for dragonfire... On 19-Aug-21 04:17, Peter John Acklam wrote: > Hi! > > I would like some input on how the Math::BigInt module and bigint pragma > should handle non-integers. The current behaviour is rather inconsistent. > > The new() constructor converts a non-integer to a Math::BigInt NaN: > > $ perl -MMath::BigInt -wle 'print Math::BigInt -> new("3.16")' > NaN > > A math operation that returns a non-integer, returns a Math::BigInt > with the > truncated value: > > $ perl -MMath::BigInt -wle 'print Math::BigInt -> new("10") -> > bsqrt()' > 3 > > Math::BigInt with overloading of constants, leave a non-integer as an > unmodified Perl scalar: > > $ perl -MMath::BigInt=:constant -wle 'print 3.16' > 3.16 > > However, when the "bigint" pragma is used for overloading constants, a > non-integer becomes a Math::BigInt with the truncated value: > > $ perl -Mbigint -wle 'print 3.16' > 3 > > I'm not saying that all four cases should return the same value, but > returning three different values seems too much. Any suggestions? > > Cheers, > Peter OpenPGP_signature Description: OpenPGP digital signature

### Re: Math::BigInt and bigint with non-integers

On Thu, Aug 19, 2021 at 4:18 AM Peter John Acklam wrote: > Hi! > > I would like some input on how the Math::BigInt module and bigint pragma > should handle non-integers. The current behaviour is rather inconsistent. > > The new() constructor converts a non-integer to a Math::BigInt NaN: > > $ perl -MMath::BigInt -wle 'print Math::BigInt -> new("3.16")' > NaN > > A math operation that returns a non-integer, returns a Math::BigInt with > the > truncated value: > > $ perl -MMath::BigInt -wle 'print Math::BigInt -> new("10") -> bsqrt()' > 3 > > Math::BigInt with overloading of constants, leave a non-integer as an > unmodified Perl scalar: > > $ perl -MMath::BigInt=:constant -wle 'print 3.16' > 3.16 > > However, when the "bigint" pragma is used for overloading constants, a > non-integer becomes a Math::BigInt with the truncated value: > > $ perl -Mbigint -wle 'print 3.16' > 3 > > I'm not saying that all four cases should return the same value, but > returning three different values seems too much. Any suggestions? > Truncation to integer seems the most useful and expected behavior to me. Not sure if the "overloading of constants" case should be affected, would people depend on it staying unmodified? -Dan