> On Dec 20, 2020, at 6:08 AM, ToddAndMargo via perl6-users
> <perl6-us...@perl.org> wrote:
>
>>> On Sun, Dec 20, 2020 at 02:05 ToddAndMargo via perl6-users
>>> <perl6-us...@perl.org <mailto:perl6-us...@perl.org>> wrote:
>>> Hi All,
>>> Why does this work?
>>> say (45*π/180).cos
>>> 0.7071067811865476
>>> And this not?
>>> say 45*π/180.cos
>>> -236.22573454917193
>>> Is not the math suppose to be done first?
>>> Confused again,
>>> -T
>
>
> On 12/20/20 3:35 AM, Tom Browder wrote:
>> (45*pi/180).cos
>
> Hi Tom,
>
> I was not asking for the how, I was asking
> for the shy one work and the other did not.
>
> Apparetly
>
> 45*π/180.cos
>
> is the same as this
>
> 45*π/(180.cos)
> -T
The unparenthesized version fails (to do what you intended) for the same reason
that this code returns 14 instead of 64:
say 5 + 3 ** 2;
Just like `**` has higher precedence than `+`, any dotted method call (like
`.cos`) has higher precedence than `*` or `/`.
(We often say “binds more tightly” instead of "has higher precedence”)
So, in this code:
$a + $b - $c * $d / $e .foo
, the .foo method is called on $e, not on the whole A-through-E sub-expression.
The subroutine form `cos()` is not a method call and not an operator, so this
will do what you meant:
say cos 45*π/180;
but also would be clearer with parens:
say cos( 45*π/180 );
For the whole precedence table, see:
https://docs.raku.org/language/operators#Operator_precedence
--
Hope this helps,
Bruce Gray (Util of PerlMonks)
