Understanding the return method

Hi,

As always, I’m asking simple questions sorry.

Please help me to understand the “return” method because I dont see
where or how to use it.
Here I’m using the return method but the thing is that if remove it, it
also works, so I was wondering why would you use it if by defaul all
methods return a value?

def multiply(val1, val2 )
result = val1 * val2
return result
end

value = multiply( 10, 20 )
puts value

Can some one show me the main purpose of using the return method?

Again I’m currently trying to understand the basics, so please be
patient : )

Thanks

2011/4/17 Fily S. [email protected]:

def multiply(val1, val2 )
result = val1 * val2
return result
end

A ruby method always returns the last object or expression it calls
internally. But if there is a return(something) within the method then
such object “something” is returned by the method. Note also that
“return” is the same as “return nil”.

In your above method, it would be the same as:

def multiply(val1, val2 )
result = val1 * val2
end

or also:

def multiply(val1, val2 )
result = val1 * val2
result
end

The advantage of using “return” is that you terminate the method when
you want without running the remaining code defined in the method.

On 2011-04-16, at 15:41, Fily S. wrote:

Hi,

As always, I’m asking simple questions sorry.
Don’t be sorry, questions need answers :).

Please help me to understand the “return” method because I dont see
where or how to use it.
Here I’m using the return method but the thing is that if remove it, it
also works, so I was wondering why would you use it if by defaul all
methods return a value?

def multiply(val1, val2 )
result = val1 * val2
return result
end

The right way to understand return is thst it’s a control operation, it
tells Ruby to exit from the procedure RIGHT NOW, with an optional return
value. So you (almost) never need it as the last step in a function (the
exception is given below), but you use it if you have the result you
need, and don’t want to execute the current procedure any more.

irb(main):001:0> def how_many_sum_to(n)
irb(main):002:1> sum = 0
irb(main):003:1> i = 1
irb(main):004:1> loop do
irb(main):005:2* sum += i
irb(main):006:2> return i if sum > n
irb(main):007:2> i += 1
irb(main):008:2> end
irb(main):009:1> end
=> nil
irb(main):010:0> how_many_sum_to(12)
=> 5

The (poorly-named) procedure keeps adding integers until it gets a value
greater than n, and returns the value that put the sum over the top.
(You can get the same answer without a loop if you do some algebra, but
that’s not relevant here.) I used a loop here rather than a while to
demonstrate that in this example the return acts like a break, exiting
the loop and the containing procedure.

irb(main):028:0> def print_square_root(x)
irb(main):029:1> if x > 0
irb(main):030:2> print(“the square root of %f is %f\n”%[x,
Math.sqrt(x)])
irb(main):031:2> return
irb(main):032:2> end
irb(main):033:1> print(“sorry, I don’t know about complex numbers
yet\n”)
irb(main):034:1> end
=> nil
irb(main):035:0> print_square_root(4)
the square root of 4.000000 is 2.000000
=> nil
irb(main):036:0> print_square_root(-4)
sorry, I don’t know about complex numbers yet
=> nil

Here we used a return to exit from a procedure early, even without a
loop.

Both of these procedures could be refactored to eliminate the need for
return. In many (most?) cases, code reads more clearly without a return
than with. The exception comes when you have perhaps several levels of
nested loops, or some rescues, or the like. So I tend to see the
presence of a return as an invitation to refactor, but there are
certainly many cases where the version with return is the clearest.

There’s one exception to the rule that a return as the last statement of
a procedure is unnecessary. If you want to return several values, you
need a return, because a comma-separated list of expressions isn’t
itself an expression.

irb(main):037:0> def return_needed(x)
irb(main):038:1> x+1, x-1
irb(main):039:1> end
SyntaxError: (irb):38: syntax error, unexpected ‘,’, expecting
keyword_end
x+1, x-1
^
from /Users/vmanis/local/bin/irb:12:in `’
irb(main):040:0> def return_needed(x)
irb(main):041:1> return x+1, x-1
irb(main):042:1> end
=> nil
irb(main):043:0> return_needed(4)
=> [5, 3]

Of course, since returning multiple values returns an array, you can
again eliminate the need for return by explicitly returning an array.

irb(main):044:0> def return_needed(x)
irb(main):045:1> [x+1, x-1]
irb(main):046:1> end

Hope this helps. – vincent

Beautiful, got it, thank you all very much for your help, it feels good
when things start to make sense and the return operator now make sense
to me.

Thanks a lot!

hi fily -

while i was answering your post, iñaki and vincent answered it much
better than i ever could have. ignore the deleted greyness, and rock
on…

jake kaiden wrote in post #993280:

hi fily -

while i was answering your post, iñaki and vincent answered it much
better than i ever could have. ignore the deleted greyness, and rock
on…

Hi jake,

There’s no need to delete your post when someone answers ahead of
you-even if you give the exact same advice. That sort of thing happens
all the time. And sometimes hearing an explanation from a fellow
beginner will make more sense than an answer from an expert.

On 2011-04-16, at 20:10, 7stud – wrote:

jake kaiden wrote in post #993280:

There’s no need to delete your post when someone answers ahead of
you-even if you give the exact same advice. That sort of thing happens
all the time. And sometimes hearing an explanation from a fellow
beginner will make more sense than an answer from an expert.

I couldn’t agree more. I appreciate the compliment about my answer, but
sometimes even saying the same thing in different words can help a
person. I’d rather see redundant answers than insufficient ones!

In any case, Jake’s answer was admirably concise, whereas mine was
anything BUT concise. So not just Fily but also anyone else who was
puzzled about return got both the brief answer AND the long-winded
one.

– vincent

All you guys are awesome… thats all I can say

2011/4/17 7stud – [email protected]:

There’s no need to delete your post when someone answers ahead of
you-even if you give the exact same advice. That sort of thing happens
all the time. And sometimes hearing an explanation from a fellow
beginner will make more sense than an answer from an expert.

Sure. In fact, sometimes is really interesting (at least for me) to
get the opinnion of people coming from other languages in which same
or similar concepts apply but in a different way.

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