Exit in a bloc DRY way

ruby-talk
1

I wrote this code that's running well..
           origin = false
           contact.each {|c| origin = true if c.from == parameter }
           nb -= 1 if origin

is there any way to write it in one line ? (exiting from the bloc when the condition is true)
something like :
           contact.each {|c| nb -= 1; exit; if c.from == parameter }

tfyl

joss

2

Hi,

I think this should do the job
nb-=1 if contact.select{|c| c==parameter}.any?

it will return nb-1 if any contact matches parameter, or nil if none match

cheers,
Dave

···

On 18/02/2007, at 10:45 PM, Josselin wrote:

I wrote this code that's running well..
          origin = false
          contact.each {|c| origin = true if c.from == parameter }
          nb -= 1 if origin

is there any way to write it in one line ? (exiting from the bloc when the condition is true)
something like :
          contact.each {|c| nb -= 1; exit; if c.from == parameter }

tfyl

joss

3

A google turns up this:

In Ruby, break exits the block with value "nil". The caller must check
after each closure call to see if the value returned was "nil", and
break itself, if necessary. A side effect is that you can't return
"nil" from a block without terminating the calling structure. (As it
happens, this is almost always acceptable.)

Use IRB to figure if indeed the standard methods that accept blocks do
this checking.

contact.each {|c| nb -= 1; exit; if c.from == parameter } # the
second ; is definitely wrong

Perhaps you meant:

contact.each {|c| if c.from == parameter; nb -= 1; break; end }

Well, if each is defined and the Enumerable mixin is mixed in (it
usually is), you get #find for free, so:

$ ri Enumerable#find
-------------------------------------------------------- Enumerable#f
ind
     enum.detect(ifnone = nil) {| obj | block } => obj or nil
     enum.find(ifnone = nil) {| obj | block } => obj or nil

···

---------------------------------------------------------------------
---
     Passes each entry in _enum_ to _block_. Returns the first for wh
ich
     _block_ is not +false+. If no object matches, calls _ifnone_ and
     returns its result when it is specified, or returns +nil+

        (1..10).detect {|i| i % 5 == 0 and i % 7 == 0 } #=> nil
        (1..100).detect {|i| i % 5 == 0 and i % 7 == 0 } #=> 35

So how about:

nb = -1 if contact.find{|c| c.from == parameter }

?

This seems good.

Plug: Have a look at the adopt-a-newbie thread

Aur Saraf

On 2/18/07, Josselin <josselin@wanadoo.fr> wrote:

I wrote this code that's running well..
           origin = false
           contact.each {|c| origin = true if c.from == parameter }
           nb -= 1 if origin

is there any way to write it in one line ? (exiting from the bloc when
the condition is true)
something like :
           contact.each {|c| nb -= 1; exit; if c.from == parameter }

tfyl

joss

4

Isn't #find better than #select?

select wouldn't break the first time a match was found, find would.
Less time, less memory.

Aur Saraf

···

On 2/18/07, Sharon Phillips <phillipsds@yahoo.co.uk> wrote:

Hi,

I think this should do the job
nb-=1 if contact.select{|c| c==parameter}.any?

it will return nb-1 if any contact matches parameter, or nil if none
match

cheers,
Dave

On 18/02/2007, at 10:45 PM, Josselin wrote:

> I wrote this code that's running well..
> origin = false
> contact.each {|c| origin = true if c.from == parameter }
> nb -= 1 if origin
>
> is there any way to write it in one line ? (exiting from the bloc
> when the condition is true)
> something like :
> contact.each {|c| nb -= 1; exit; if c.from == parameter }
>
> tfyl
>
> joss
>

5

thanks a lot !! I love Ruby for that.... start from one point .. and logically go to the DRY way... with
Rubist help....

where is this thread 'adopt a newbie' .... ?

joss

···

On 2007-02-18 13:05:29 +0100, SonOfLilit <sonoflilit@gmail.com> said:

A google turns up this:

In Ruby, break exits the block with value "nil". The caller must check
after each closure call to see if the value returned was "nil", and
break itself, if necessary. A side effect is that you can't return
"nil" from a block without terminating the calling structure. (As it
happens, this is almost always acceptable.)

Use IRB to figure if indeed the standard methods that accept blocks do
this checking.

contact.each {|c| nb -= 1; exit; if c.from == parameter } # the
second ; is definitely wrong

Perhaps you meant:

contact.each {|c| if c.from == parameter; nb -= 1; break; end }

Well, if each is defined and the Enumerable mixin is mixed in (it
usually is), you get #find for free, so:

$ ri Enumerable#find
-------------------------------------------------------- Enumerable#f
ind
     enum.detect(ifnone = nil) {| obj | block } => obj or nil
     enum.find(ifnone = nil) {| obj | block } => obj or nil
---------------------------------------------------------------------
---
     Passes each entry in _enum_ to _block_. Returns the first for wh
ich
     _block_ is not +false+. If no object matches, calls _ifnone_ and
     returns its result when it is specified, or returns +nil+

        (1..10).detect {|i| i % 5 == 0 and i % 7 == 0 } #=> nil
        (1..100).detect {|i| i % 5 == 0 and i % 7 == 0 } #=> 35

So how about:

nb = -1 if contact.find{|c| c.from == parameter }

?

This seems good.

Plug: Have a look at the adopt-a-newbie thread

Aur Saraf

On 2/18/07, Josselin <josselin@wanadoo.fr> wrote:

I wrote this code that's running well..
           origin = false
           contact.each {|c| origin = true if c.from == parameter }
           nb -= 1 if origin

is there any way to write it in one line ? (exiting from the bloc when
the condition is true)
something like :
           contact.each {|c| nb -= 1; exit; if c.from == parameter }

tfyl

joss

6

I'd do:

  nb-=1 if contact.any?{|c| c.from==parameter}

Regards,
George.

···

On 2/18/07, SonOfLilit <sonoflilit@gmail.com> wrote:

On 2/18/07, Sharon Phillips <phillipsds@yahoo.co.uk> wrote:
> Hi,
>
> I think this should do the job
> nb-=1 if contact.select{|c| c==parameter}.any?
>
> it will return nb-1 if any contact matches parameter, or nil if none
> match
>
> cheers,
> Dave
Isn't #find better than #select?

select wouldn't break the first time a match was found, find would.
Less time, less memory.

Aur Saraf

7

Isn't #find better than #select?

Yes, I think you are correct.
I am learning too and had not come across find before. Thankyou for the information.

Cheers,
Dave

···

On 18/02/2007, at 11:06 PM, SonOfLilit wrote:

Isn't #find better than #select?

select wouldn't break the first time a match was found, find would.
Less time, less memory.

Aur Saraf

On 2/18/07, Sharon Phillips <phillipsds@yahoo.co.uk> wrote:

Hi,

I think this should do the job
nb-=1 if contact.select{|c| c==parameter}.any?

it will return nb-1 if any contact matches parameter, or nil if none
match

cheers,
Dave

On 18/02/2007, at 10:45 PM, Josselin wrote:

> I wrote this code that's running well..
> origin = false
> contact.each {|c| origin = true if c.from == parameter }
> nb -= 1 if origin
>
> is there any way to write it in one line ? (exiting from the bloc
> when the condition is true)
> something like :
> contact.each {|c| nb -= 1; exit; if c.from == parameter }
>
> tfyl
>
> joss
>

8

Here in the list. How do you read the list? Myself, I'm subscribed to
it in my gmail account and have it all in a label, so for me it's
simply in the first page.

If you can't find it, google for ruby adopt-a-newbie.

Aur Saraf

···

On 2/18/07, Josselin <josselin@wanadoo.fr> wrote:

On 2007-02-18 13:05:29 +0100, SonOfLilit <sonoflilit@gmail.com> said:

> A google turns up this:
>
> In Ruby, break exits the block with value "nil". The caller must check
> after each closure call to see if the value returned was "nil", and
> break itself, if necessary. A side effect is that you can't return
> "nil" from a block without terminating the calling structure. (As it
> happens, this is almost always acceptable.)
>
> Use IRB to figure if indeed the standard methods that accept blocks do
> this checking.
>
> contact.each {|c| nb -= 1; exit; if c.from == parameter } # the
> second ; is definitely wrong
>
> Perhaps you meant:
>
> contact.each {|c| if c.from == parameter; nb -= 1; break; end }
>
> Well, if each is defined and the Enumerable mixin is mixed in (it
> usually is), you get #find for free, so:
>
> $ ri Enumerable#find
> -------------------------------------------------------- Enumerable#f
> ind
> enum.detect(ifnone = nil) {| obj | block } => obj or nil
> enum.find(ifnone = nil) {| obj | block } => obj or nil
> ---------------------------------------------------------------------
> ---
> Passes each entry in _enum_ to _block_. Returns the first for wh
> ich
> _block_ is not +false+. If no object matches, calls _ifnone_ and
> returns its result when it is specified, or returns +nil+
>
> (1..10).detect {|i| i % 5 == 0 and i % 7 == 0 } #=> nil
> (1..100).detect {|i| i % 5 == 0 and i % 7 == 0 } #=> 35
>
> So how about:
>
> nb = -1 if contact.find{|c| c.from == parameter }
>
> ?
>
> This seems good.
>
> Plug: Have a look at the adopt-a-newbie thread
>
> Aur Saraf
>
> On 2/18/07, Josselin <josselin@wanadoo.fr> wrote:
>> I wrote this code that's running well..
>> origin = false
>> contact.each {|c| origin = true if c.from == parameter }
>> nb -= 1 if origin
>>
>> is there any way to write it in one line ? (exiting from the bloc when
>> the condition is true)
>> something like :
>> contact.each {|c| nb -= 1; exit; if c.from == parameter }
>>
>> tfyl
>>
>> joss

thanks a lot !! I love Ruby for that.... start from one point .. and
logically go to the DRY way... with
Rubist help....

where is this thread 'adopt a newbie' .... ?

joss

9

I'd do:

  nb-=1 if contact.any?{|c| c.from==parameter}

Regards,
George.

Wow, #any? can do this? Thanks for teaching me a cool idiom!

···

On 2/18/07, George Ogata <george.ogata@gmail.com> wrote:

On 2/18/07, Sharon Phillips <phillipsds@yahoo.co.uk> wrote:

Yes, I think you are correct.
I am learning too and had not come across find before. Thankyou for
the information.

Cheers,
Dave

Then let me repeat that plug: Check out the adopt-a-newbie thread please :slight_smile:

Aur Saraf