perl6 / rakudo：如何更改变量的数据类型？

Question

#!perl6
use v6;

my $m = 70;
my $n = 30;

( $m div $n ).say;

.

第一个示例工作，但第二个例子没有。我想它是因为在第二个例子中，变量值是字符串。如果我的猜测是对的，我如何将字符串变量更改为整数变量？

#!perl6
use v6;

my $m = '70';
my $n = '30';

( $m div $n ).say;


# No applicable candidates found to dispatch to for 'infix:<div>'. 
# Available candidates are:
# :(Int $a, Int $b)

#   in main program body at line 7:./perl5.pl

.

Answer 1

You can always manually cast to Int

( $m.Int div $n.Int ).say;

Actually I would have hoped that prefix:<+> would work as in

( +$m div +$n ).say;

But it just "Num"ifies and the sig requires "Int", I am not sure if it should be this way or not.

UPDATE: +$m now works.

Answer 2

I kinda think that the second form should work too (coerce to Int first, and then do integer division). I'll get some feedback from the other Perl 6 developers, and fix it if they agree. (Update: turns out that infix: is explicitly not coercive, but rather is specced to return a value of the same type as the arguments. Which won't work for generally for Str).

As Pat pointed out, +$m should also work, that's a long standing limitation in Rakudo.

In general, coercion to a type is done with $variable.Typename, and I believe this works for all numeric types in Rakudo today.