Confusion over "mutators" in section 4
MattOates opened this issue · comments
http://perl6intro.com/#_functions_and_mutators this section is really quite confusing and has indeed caused confusion already https://www.reddit.com/r/perl6/comments/3vjuex/how_to_easily_tell_the_difference_between_a/
I was thinking of enhancing this section by replacing it with:
https://gist.github.com/hankache/66f43377f5a6393a11646beed748c0cc
@MattOates would it become less confusing?
@lizmat @zoffixznet can you kindly review?
Looks more or less right, depending on how pedantic you want to get; like "The number 3 [...] will never change over time" is not quite true for Rakudo:
<Zoffix___> m: BEGIN 3 does role { method Bridge { 42 } }; say 3 + 2e0
<camelia> rakudo-moar 639c6da0c: OUTPUT: «44»
The references explanation is very different from how all that stuff fits into my brain—not implying that it's wrong, just different.
I don't think in terms of mutable-immutable references (that's reminiscent of Rust's ownership), but in terms of containers. my $a = 42; $a = 42 works, because there's a Scalar container and I'm storing a new value in that container. my $a := 42; $a = 42 throws, because there's no container, so there's nothing to store the new value into. More in my containers article: https://perl6advent.wordpress.com/2017/12/02/
The one thing I do see as potential for confusion is sentence "Trying to change the value of a constant leads to an error" since it implies the constant offers some sort of mutability protection, but it doesn't. If I stick a container or a mutable object into a constant, I can change the value all I want:
<Zoffix___> m: constant FOO = $ = 42; say FOO; FOO = 100; say FOO
<camelia> rakudo-moar 639c6da0c: OUTPUT: «42100»
<Zoffix___> m: constant FOO = [<a b c>]; say FOO; FOO[1] = 'meows'; say FOO
<camelia> rakudo-moar 639c6da0c: OUTPUT: «[a b c][a meows c]»
A constant is very much like a variable that doesn't auto-give a container (like my \foo) except its initializer is run at compile time. So it's fairly easy to get a constant isn't actually constant.
@zoffixznet I think you're right. This whole mutable/immutable feels alien to Perl 6. I should find a way to explain containers in a friendly manner to people new to Perl 6.
Thank you for your feedback.
I suggest renaming the 4 section into "Methods and mutators"