An interview with Larry Wall (LinuxVoice)

I can't imagine any language doing that. If your comment is aimed at Perl (5 or 6) then I think this is another manifestation of overall confusion about decimal fractions.

https://en.wikipedia.org/wiki/Decimal#Decimal_fractions

> Merely writing "3.14159" makes perl6 treat it as 314159/100000.

Just for emphasis: https://en.wikipedia.org/wiki/Decimal#Decimal_fractions

Hopefully you'll spend a few seconds reading this wikipedia link and you'll go "ahhh". :)

> What happens when interfacing with a C library (say GSL)?

One uses explicit typing in the signature (the list of parameters) of the Perl 6 functions that call the C functions. For example:

sub add(int32, int32) returns int32 is native("libcalculator") { * }

means that one must call the `add` function with two native 32 bit ints.

See http://doc.perl6.org/language/nativecall#Passing_and_Retu... for some more details.

> Are these "rationals" then converted into floats before calling?

They can be. It's controlled by explicit types and explicit type coercions in the signature. For example:

sub foo(Num(Rat), Num) ...

would be callable with:

foo(13/17, 26e3)

> And are the return values converted back to "rationals"?

Rakudo does not currently support signature based coercion of the return value; I don't know whether there's a plan to one day support that.