Re^9: Small Perl 6 discoveries II, Rats

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Re^10: Small Perl 6 discoveries II, Rats by holli (Abbot) on Oct 25, 2017 at 01:43 UTC
Yeah, well. That is to be expected as it is akin to assigning an int64 to an int32. What surprises me is that `perl6 -e "my FatRat $r = 0.1"` [download] throws the same error. holli You can lead your users to water, but alas, you cannot drown them.	[reply] [d/l]
Re^11: Small Perl 6 discoveries II, Rats by raiph (Deacon) on Oct 27, 2017 at 18:38 UTC
First, Rats aren't FatRats and vice-versa. (If we need to discuss why, we'll need to start with Larry's comment that "we've intentionally steered clear of any sort of numeric tower"; and then dig into what p6curious meant when they followed that up with "its one of the things that has impressed me the most about perl6"; and then consider Rats and FatRats in particular.) Second, P6 has a nice feature that directly addresses this. It has been implemented for routine parameters but not yet `my` declarations: `sub fails-if-passed-Rat (FatRat $r) { say WHAT $r } ; sub works-if-passed-number (FatRat() $r) { say WHAT $r } ; fails-if-passed-Rat 1.0 ; # typecheck failure works-if-passed-number 1.0 ; # coerces 1.0 to a FatRat my FatRat $r = 1.0 ; # typecheck failure my FatRat() $r = 1.0 ; # should say "not yet implemented"` [download]	[reply] [d/l]
Re^12: Small Perl 6 discoveries II, Rats by Anonymous Monk on Oct 27, 2017 at 19:05 UTC
First, `Rats` aren't `FatRats` and vice-versa. They're both `Rational`, but that's still not very useful. `> my Rational $x = 1.111111111111111111111; 1.11111111111111111604544 > $x *= 0.1; Type check failed in assignment to $x; expected Rational but got Num ( +0.111111111111111e0)` [download] The argument type-coercion is cute, but there doesn't seem to be any way to set the precision. `> sub foo(FatRat() $x) { return $x }; foo(pi).nude (355 113) > pi.FatRat(1e-8).nude (103993 33102)` [download] And I don't know how to interpret this message... `> my FatRat() $x = 0.1; ===SORRY!=== Error while compiling: Coercion FatRat(Any) is insufficiently type-like to qualify a variable ------> my FatRat() $x⏏ = 0.1; expecting any of: constraint` [download]	[reply] [d/l] [select]
Re^13: Small Perl 6 discoveries II, Rats by raiph (Deacon) on Oct 27, 2017 at 20:19 UTC
Re^14: Small Perl 6 discoveries II, Rats by Anonymous Monk on Oct 28, 2017 at 06:35 UTC
Re^10: Small Perl 6 discoveries II, Rats by syphilis (Archbishop) on Oct 25, 2017 at 02:54 UTC
Type check failed in assignment to $x; expected Rat but got FatRat At least that Rat appears to be immutable ;-) I need to study the documentation and spend some time working through it. Cheers, Rob	[reply]
Re^11: Small Perl 6 discoveries II, Rats by raiph (Deacon) on Oct 27, 2017 at 19:03 UTC
I do think studying the doc and working through it is the way to go but in the meantime, for anyone else reading along, I may be missing a joke here (given Rob's wink smiley), but to be humorless but hopefully clear, all Rats are immutable, as explained in my ancestor comment.	[reply]
Re^10: Small Perl 6 discoveries II, Rats by raiph (Deacon) on Oct 27, 2017 at 19:25 UTC
It makes sense that the compiler would be disappointed but that's because you told it to expect a Rat on the LHS but then put a FatRat on the RHS and "Arithmetic operations involving a FatRat and optionally Int or Rat objects return a FatRat, avoiding loss of precision."	[reply]
Re^11: Small Perl 6 discoveries II, Rats by Anonymous Monk on Oct 28, 2017 at 06:48 UTC
What, then, should I declare as the type of my variable? There seems to be no good choice.	[reply]