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0 pointskstrauser5mo ago0 comments

For me personally, the biggest pain points that drove me to Python were:

1. Sigils, and relatedly, contexts. In my opinion, `my $length = @list;` is a horrid way to spell `length = len(list)`. It feels too much like typecasting magic.

2. Having to opt in to pass by reference caused so much pain. You're happily passing a hash around, but then you want to do something to it, so now you have to change the type signature of the function, then everything that calls it, etc. etc.

Contrast with Python, where everything is pass-by-object-reference and sigils aren't needed because contexts in the Perl sense don't exist. This worked on my first try:

  >>> a = ["foo", 123, {"bar": [(1,2,3), {"qux": "quux"}]}]
  >>> a[2]["bar"][1]["spam"] = "eggs"
  >>> import json
  >>> json.dumps(a)

I liked Perl. I wrote a lot of Perl. And yet, I still had to pull out The Book whenever I wanted to do anything more complex than passing a couple of ints or strings around. This stuff is knowable, obviously, but I just got tired of having to know it.

0 comments

Ultimatt5mo ago

I haven't touched Perl in about ten years but your example is kind of insane. This is the one place Python is more annoying than Perl???

    my $a = ["foo", 123, {"bar" => [[1,2,3], {"qux" => "quux"}]}];
    $a->[2]{"bar"}[1]{"spam"} = "eggs";
    use JSON;
    print(encode_json($a))

That's the same as your example (minus the tuple type), but where Perl shines over Python (a lot) is you could have done the following:

    use JSON;
    my $a = [];
    $a->[2]{"bar"}[1]{"spam"} = "eggs";
    print(encode_json($a))

which would yield the json: [null,null,{"bar":[null,{"spam":"eggs"}]}]

To do this in Python is truly grim:

    import json
    from collections import defaultdict

    # recursive defaultdict using lambda
    datastructure = lambda: defaultdict(datastructure)

    a = [None] * 3
    a[2] = datastructure()
    a[2]["bar"][1]["spam"] = "eggs"

    print(json.dumps(a))

and thats doing it the unpythonic way, if you were to do this like the typical Python dev would accept in an MR for a large corp you would have written:

    import json
    from collections import defaultdict

    def datastructure():
       return defaultdict(datastructure)

    a = []
    # expand list to at least length 3
    while len(a) < 3:
       a.append(None)
 
    a[2] = datastructure()
    a[2]["bar"][1]["spam"] = "eggs"

    print(json.dumps(a))

They would still hate you for defaultdict(datastructure) though. Because absolutely no one in Python realises its got that level of expressionism one of the few places it does.

kstrauserOP5mo ago

Why is there an arrow between $a and [2], but not between [2] and {“bar”}, in this?

  $a->[2]{"bar"}

The highest rated SO answer here explains a little, and it’s the kind of situational nitpickiness that let to me dropping Perl like a hot potato when something better matching my mental model came across my radar: https://stackoverflow.com/questions/1817394/whats-the-differ...

Enk1du5mo ago

I suppose it's because very soon people got tired of writing

  $a->[2]->{"bar"}

which is equivalent and also works, but suffers from the explosion of punctuation that Perl often gets criticised for. There's an element of Do What I Mean where the first arrow says this is a reference and work the rest out for me.

odc5mo ago

In Perl -> is the dereference operator, similar to C.

So when you see

    $a->[2]{"bar"}

then $a is an array reference where each item is a hashmap. But with

    $a->[2]->{"bar"}

then $a is an array reference where each item is a reference to a hashmap.

1 more reply

hackthemack5mo ago

Programming is such a strange field with so many people with different mental models. I am no fan of Perl, but I think having a function pass arguments as copies (and then also having semantics to work on the original by reference if you want to) is very handy. Passing copies reduces side effects.

kstrauserOP5mo ago

There are any number of ways to skin that cat. In Rust, for example, values you pass, whether by value or by reference, are immutable by default. You have to explicitly mark them as mutable in the receiving function signature to allow mutation. I freaking love that as a default. Passing by reference is trivially easy, but you still avoid accidentally altering things that ought not be frobnicated.

davidschultz5mo ago

In this case it might interest you to learn that in Raku (Perl 6), the values passed to a function are also by default immutable within that function.

If one wants the function to mutate them, one has to explicitly mark them as `$x is rw` in the function signature; this then requires one to always pass a mutable container for $x. (A bit more detail: https://andrewshitov.com/2019/10/15/110-is-rw-vs-is-raw-in-r... )

1 more reply

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0 pointskstrauser5mo ago0 comments

For me personally, the biggest pain points that drove me to Python were:

1. Sigils, and relatedly, contexts. In my opinion, `my $length = @list;` is a horrid way to spell `length = len(list)`. It feels too much like typecasting magic.

Contrast with Python, where everything is pass-by-object-reference and sigils aren't needed because contexts in the Perl sense don't exist. This worked on my first try:

  >>> a = ["foo", 123, {"bar": [(1,2,3), {"qux": "quux"}]}]
  >>> a[2]["bar"][1]["spam"] = "eggs"
  >>> import json
  >>> json.dumps(a)

0 comments

Ultimatt5mo ago

I haven't touched Perl in about ten years but your example is kind of insane. This is the one place Python is more annoying than Perl???

    my $a = ["foo", 123, {"bar" => [[1,2,3], {"qux" => "quux"}]}];
    $a->[2]{"bar"}[1]{"spam"} = "eggs";
    use JSON;
    print(encode_json($a))

That's the same as your example (minus the tuple type), but where Perl shines over Python (a lot) is you could have done the following:

    use JSON;
    my $a = [];
    $a->[2]{"bar"}[1]{"spam"} = "eggs";
    print(encode_json($a))

which would yield the json: [null,null,{"bar":[null,{"spam":"eggs"}]}]

To do this in Python is truly grim:

    import json
    from collections import defaultdict

    # recursive defaultdict using lambda
    datastructure = lambda: defaultdict(datastructure)

    a = [None] * 3
    a[2] = datastructure()
    a[2]["bar"][1]["spam"] = "eggs"

    print(json.dumps(a))

and thats doing it the unpythonic way, if you were to do this like the typical Python dev would accept in an MR for a large corp you would have written:

    import json
    from collections import defaultdict

    def datastructure():
       return defaultdict(datastructure)

    a = []
    # expand list to at least length 3
    while len(a) < 3:
       a.append(None)
 
    a[2] = datastructure()
    a[2]["bar"][1]["spam"] = "eggs"

    print(json.dumps(a))

They would still hate you for defaultdict(datastructure) though. Because absolutely no one in Python realises its got that level of expressionism one of the few places it does.

kstrauserOP5mo ago

Why is there an arrow between $a and [2], but not between [2] and {“bar”}, in this?

  $a->[2]{"bar"}

Enk1du5mo ago

I suppose it's because very soon people got tired of writing

  $a->[2]->{"bar"}

odc5mo ago

In Perl -> is the dereference operator, similar to C.

So when you see

    $a->[2]{"bar"}

then $a is an array reference where each item is a hashmap. But with

    $a->[2]->{"bar"}

then $a is an array reference where each item is a reference to a hashmap.

1 more reply

hackthemack5mo ago

kstrauserOP5mo ago

davidschultz5mo ago

In this case it might interest you to learn that in Raku (Perl 6), the values passed to a function are also by default immutable within that function.

1 more reply

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