Surprising(?) behaviour of the comma operator

[Frank Schmitt]

Hi!

I just stumbled over a (at least for me) surprising behaviour
of the comma (',') operator:

irb(main):001:0> a,b = 1,2
[1, 2]
irb(main):002:0> puts a.class, b.class
Fixnum
Fixnum
nil

Ok, no surprises so far. Here we go:

irb(main):003:0> a=1, b=2
[1, 2]
irb(main):004:0> puts a.class, b.class
Array
Fixnum
nil

that is, a=1, b=2 creates an *Array* a instead of a Fixnum.
I don't think this is a bug, since others surely have spotted
this before me, but what's the rationale behind this?

kind regards
frank

 

[nobu.nokada]

Hi,

At Mon, 8 Dec 2003 18:32:03 +0900,

I just stumbled over a (at least for me) surprising behaviour
of the comma (',') operator:

Ruby has no comma operator like C.

irb(main):003:0> a=1, b=2
[1, 2]
irb(main):004:0> puts a.class, b.class
Array
Fixnum
nil

If you really want to use multi-statement, use semicolon (
instead.

 

[Hal Fulton]

Hi,

At Mon, 8 Dec 2003 18:32:03 +0900,

I just stumbled over a (at least for me) surprising behaviour
of the comma (',') operator:

Ruby has no comma operator like C.

irb(main):003:0> a=1, b=2
[1, 2]
irb(main):004:0> puts a.class, b.class
Array
Fixnum
nil

If you really want to use multi-statement, use semicolon (
instead.

Correct of course. To clarify a little for the original poster,
the statement is equivalent to:

a = [1, b=2]



Hal

 

[Frank Schmitt]

Hi,

At Mon, 8 Dec 2003 18:32:03 +0900,

I just stumbled over a (at least for me) surprising behaviour
of the comma (',') operator:

Ruby has no comma operator like C.

irb(main):003:0> a=1, b=2
[1, 2]
irb(main):004:0> puts a.class, b.class
Array
Fixnum
nil

If you really want to use multi-statement, use semicolon (
instead.

Normally I don't use multi-statements, but (coming from C++) I
wrote

def initialize(a,b)
@a = a, @b = b
end

Writing

def initialize(a,b)
@a,@b = a,b
end

instead is no big deal, I just have to remember it

Thanks to all for the quick responses & kind regards
frank