Hi All,
I’m a little confused about why the following two pieces of code seem
to behave differently:
if $val =~ /this/i
puts “this”
elseif $val =~ /that/i
puts “that”
elseif $val =~ /the other/i
puts “the other”
end
if $val contains “this is the other value”, for some reason “the
other” is not put by the last elseif statement. However, the following
code works as expected:
if $val =~ /this/i
puts “this”
end
if $val =~ /that/i
puts “that”
end
if $val =~ /the other/i
puts “the other”
end
Am I missing something about if / elseif in ruby?
Any help appreciated!
pt
On Mar 15, 9:59 am, “planetthoughtful” [email protected]
wrote:
Am I missing something about if / elseif in ruby?
Obviously I was missing something - the correct syntax. I’m now aware
that the syntax should be “elsif” rather than “elseif”.
Thanks all,
pt
planetthoughtful wrote:
On Mar 15, 9:59 am, “planetthoughtful” [email protected]
wrote:
Am I missing something about if / elseif in ruby?
Obviously I was missing something - the correct syntax. I’m now aware
that the syntax should be “elsif” rather than “elseif”.
Thanks all,
pt
You’re not the only one. I wasn’t quite so generous:
http://www.ruby-forum.com/topic/100350#new
On Thu, Mar 15, 2007 at 12:12:17PM +0900, Augie De Blieck Jr. wrote:
it prints “this,” it stops looking at any of the other “elsif”
statements.
That short circuiting is a feature. =)
Indeed – that’s the whole point of using elsif rather than just a list
of separate if statements. The if/elsif/else construct is used for
mutually exclusive flow control, where only one of several is to be
executed. Using a series of if statements considers each in a vacuum,
in order, while if/elsif/else considers them all as part of a greater
whole.
if $val =~ /this/i
puts “this”
elseif $val =~ /that/i
puts “that”
elseif $val =~ /the other/i
puts “the other”
end
Just remember that even when you spell it right, it’s going to drop
out of the whole construct just as soon as it fulfills a RegEx. After
it prints “this,” it stops looking at any of the other “elsif”
statements.
That short circuiting is a feature. =)
-Augie
On Mar 15, 1:12 pm, “Augie De Blieck Jr.” [email protected] wrote:
it prints “this,” it stops looking at any of the other “elsif”
statements.
Yes, that was the behaviour I was looking for. I noticed I provided an
ambiguous example in that in another construct it would possibly have
matched two different conditions. However, in my actual script I am
looking for values that are mutually exclusive, so exiting on finding
a value is fine.
All the best,
pt
So it doesn’t work like the C variety?
if ( condition )
statement // maybe done
else if ( condition )
statement // or maybe done
else
statement // done if the 1st and 2nd are not done
Honestly, my biggest difficulties so far are that I think of code
somewhere between C and PHP (I like to call it a nicer C)
On Thu, Mar 15, 2007 at 02:41:53PM +0900, John J. wrote:
So it doesn’t work like the C variety?
if ( condition )
statement // maybe done
else if ( condition )
statement // or maybe done
else
statement // done if the 1st and 2nd are not done
Err . . . I’m pretty sure if, elsif, else works exactly like the C if,
else if, else.
Hi –
On 3/15/07, Chad P. [email protected] wrote:
Err . . . I’m pretty sure if, elsif, else works exactly like the C if,
else if, else.
Pretty much, except in Ruby there’s no need for a rule to resolve
if/else ambiguity, because ‘end’ always makes it clear.
David
On Sat, Mar 17, 2007 at 07:20:42AM +0900, David A. Black wrote:
else
statement // done if the 1st and 2nd are not done
Err . . . I’m pretty sure if, elsif, else works exactly like the C if,
else if, else.
Pretty much, except in Ruby there’s no need for a rule to resolve
if/else ambiguity, because ‘end’ always makes it clear.
Thanks for adding that. I had forgotten about that, largely because I
haven’t written a line of C/C++ in about five years.
I imagine there are other differences as well, but for the general case
I haven’t run across any (yet). Still new to Ruby, may just not have
encountered further differences yet.
On Mar 14, 5:59 pm, “planetthoughtful” [email protected]
wrote:
I’m a little confused about why the following two pieces of code seem
to behave differently:
if $val =~ /this/i
puts “this”
elseif $val =~ /that/i
puts “that”
elseif $val =~ /the other/i
puts “the other”
end
Thought I’d point out that Ruby’s case statement is more powerful than
many other languages’ switch statements:
%w| pthisic thatch mother armadillo |.each{ |val|
case val
when /this/i
puts “‘#{val}’ contains ‘this’”
when /that/i
puts “‘#{val}’ contains ‘that’”
when /other/i
puts “‘#{val}’ contains ‘other’”
else
puts “‘#{val}’ does not contain ‘this’, ‘that’, or ‘other’”
end
}
#=> ‘pthisic’ contains ‘this’
#=> ‘thatch’ contains ‘that’
#=> ‘mother’ contains ‘other’
#=> ‘armadillo’ does not contain ‘this’, ‘that’, or ‘other’
Also, note (as seen above) that the regexp you supplied as example
match substrings even inside words. Just in case you wanted exact case-
insenstive string matching, perhaps /\Athis\Z/i would be more
appropriate. If you wanted exact word matching, perhaps /\bthis\b/i
might be what you want.