Simple syntax question

Rails
1

In:

=== code start ====
a=10, b=20
c=100, d=2200
#x=>1000, y=>2000 # MultipleExpressionsPerLine.rb:3:

p a, b
p c, d
=== code end ===

Ruby puts out four lines (under SciTE):

[10, 20]
20
[100, 2200]
2200

Q1: Why does Ruby somehow create an array for lines 1 & 2?
Q2: Why does Ruby assign this array to a, but the scalar (20) to b?
Q3: If Ruby’s willing to build arrays for lines 1 & 2, why won’t it
build a hash for line 3?

I’m running WinXP-Pro/SP2, Ruby 1.8.2-15, Rails 1.1.6.

2

Hi –

On Fri, 15 Dec 2006, Richard wrote:

=== code end ===
Q3: If Ruby’s willing to build arrays for lines 1 & 2, why won’t it
build a hash for line 3?

I’m running WinXP-Pro/SP2, Ruby 1.8.2-15, Rails 1.1.6.

When you do this:

a=10, b=20

the way it’s parsed is:

a = 10, (b=20)

The assignment of 20 to b happens first, and then the whole rhs is
assigned to a. From a’s point of view, this is the same as:

a = 10,20

and assigning a literal list like that works like assigning an array.

As for the third line: x => 1000 isn’t a legal expression on its own.
=> is not an assignment operator; it’s just a hash key/value
separator.

David

–
Q. What’s a good holiday present for the serious Rails developer?
A. RUBY FOR RAILS by David A. Black (Ruby for Rails)
aka The Ruby book for Rails developers!
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

3

Hi David,

Thanks for your clarification. Now that you explain (a=10, b=20), my
brain said: You read that before, Dummy … why do you always forget
things?

I had just found a nice tutorial on sorting tables by clicking on
column headings. It included a long line of comma-separated
assignments and I couldn’t make sense of it. Now I’m grounded again!

Again, thanks.

Best wishes,
Richard