Crystal: explicit the function call syntax and overloading problem

[hzqd]

Try this code:

a = 1

def a() 
    2
end

puts a      # 1
puts a()    # 2

I think this is correct, for a is a value, and a() is a function.

There are many programming languages not support this feature, so I'm very happy when I saw it.

But, try this code:

def a() 
    2
end

puts a  # output: 2

It shouldn't be compiled, for a is a value, not a function or closure. This can lead to syntax inconsistencies and confusion.

And, try this code:

puts a()  # output 3

def a() 
    2
end

def a()
    3
end

puts a()  # output 3

It shouldn't be compiled too, for the two functions are not overloaded relationships: they have the same parameter and return type.

[sudo-nice]

You might be thinking as a Pythonist, were you a Rubyist, that would make sense for you.

[z64]

Parentheses are optional for method calls in Crystal. So, in the first two examples, when you have a identifier that could be a local variable or a method call, the local variable is preferred.
Then, the syntax of a() is unambiguously a method call.

In the last example, this is a feature of the language to be able to override, or re-define methods by defining one with the same name and signature. See the reference.

[jhass]

This is all by design and I'm afraid we're past a stage where we would change the language so fundamentally :)

[straight-shoota]

To clarify:

It shouldn't be compiled, for a is a value, not a function or closure. This can lead to syntax inconsistencies and confusion.

In Crystal, a is either a reference to a variable a or a call to method a (in case no such variable exists in the local scope). That might look concerning, but in practice it's actually not a relevant issue. Neither in Ruby nor Crystal.

And I think this kind of makes sense. There is really not much difference in whether you're referring to a local variable or, for example a property of an object. Both can be accessed by the same syntax. And properties are just methods, which is a very simple concept.

[RX14]

If you have any more questions on how/why the language works, then I suggest you head over to https://forum.crystal-lang.org/. We'll be happy to explain the design decisions!