[#395238] rubygem: ispunity (unite all your internet connections) — Arun Tomar <tomar.arun@...>

Dear friends,

12 messages 2012/05/01

[#395250] Overwriting one Ruby array or arrays with another — Craig Law <lists@...>

Hi

14 messages 2012/05/02

[#395258] array of strings - finding letter combinations — "Sebastjan H." <lists@...>

Hi All,

16 messages 2012/05/02

[#395357] Why Enumerator#next does not return more than one value? — Földes László <lists@...>

If I have an Enumerator which yields elements of a mathematical series

10 messages 2012/05/07

[#395373] How to use Data_Wrap_Struct to assign the DATA VALUE to an exsiting Ruby object? — Iñaki Baz Castillo <ibc@...>

Hi, my code receives an arbitrary klass name (provided by the user)

8 messages 2012/05/07

[#395429] passing via instance variable or regular () — sam jam <lists@...>

def first

10 messages 2012/05/10

[#395463] I'm looking for a Metaprogramming Project — Phil Stone <lists@...>

Hello,

19 messages 2012/05/11

[#395548] A million reasons why Encoding was a mistake — Marc Heiler <lists@...>

Newcomer wants to try Ruby.

15 messages 2012/05/15
[#395561] Re: A million reasons why Encoding was a mistake — Ryan Davis <ryand-ruby@...> 2012/05/15

[#395595] Re: A million reasons why Encoding was a mistake — Brian Candler <lists@...> 2012/05/16

I will add that the OP is not entirely alone in his opinion.

[#395551] How to ensure that a block runs entirely after other threads? (Thread.exclusive does not "work") — Iñaki Baz Castillo <ibc@...>

Hi, I expected that in the following example code, thread t1 would not

8 messages 2012/05/15

[#395575] GUI with ruby on windows — David Acosta <lists@...>

hello friends, i am a begginer and i have a litlle question, how can i

17 messages 2012/05/16

[#395604] what is going wrong here? — roob noob <lists@...>

Notice the initialization of both classes in each of the examples, if

20 messages 2012/05/16

[#395646] rb_gc_register_address() or rb_gc_mark()? — Iñaki Baz Castillo <ibc@...>

Hi, I've bad experiences with rb_gc_register_address(), it does never

16 messages 2012/05/17

[#395686] reading from and writing to a Unicode encoded file — "Sebastjan H." <lists@...>

Hi,

19 messages 2012/05/18
[#395694] Re: reading from and writing to a Unicode encoded file — Regis d'Aubarede <lists@...> 2012/05/18

Hello,

[#395697] Re: reading from and writing to a Unicode encoded file — "Sebastjan H." <lists@...> 2012/05/18

Regis d'Aubarede wrote in post #1061272:

[#395698] Re: reading from and writing to a Unicode encoded file — Regis d'Aubarede <lists@...> 2012/05/18

Sebastjan H. wrote in post #1061276:

[#395699] Re: reading from and writing to a Unicode encoded file — "Sebastjan H." <lists@...> 2012/05/18

Regis d'Aubarede wrote in post #1061277:

[#395750] Re: reading from and writing to a Unicode encoded file - issues when using Shoes — "Sebastjan H." <lists@...> 2012/05/21

Hi,

[#395754] Re: reading from and writing to a Unicode encoded file - issues when using Shoes — "Sebastjan H." <lists@...> 2012/05/21

Sebastjan H. wrote in post #1061483:

[#395740] ? Ruby through CGI and Rails — Shaun Lloyd <list@...>

Hi everybody,

22 messages 2012/05/21
[#395764] Re: Ruby through CGI and Rails — Brian Candler <lists@...> 2012/05/21

Shaun Lloyd wrote in post #1061455:

[#395786] Re: Ruby through CGI and Rails — Shaun Lloyd <list@...> 2012/05/22

On 22/05/12 03:37, Brian Candler wrote:

[#395838] Re: Ruby through CGI and Rails — Brian Candler <lists@...> 2012/05/23

Shaun Lloyd wrote in post #1061602:

[#395787] Changing self class from inside a method?? — David Madison <lists@...>

Let's start off with the assumption I want a method that allows an

10 messages 2012/05/22

[#395841] Memory-efficient set of Fixnums — George Dupre <lists@...>

Hi,

25 messages 2012/05/23

[#395883] looking for a ruby idiom : r=foo; return r if r — botp <botpena@...>

Hi All,

11 messages 2012/05/24

[#395966] Am I justified to use a global variable if it must be used in all scopes? — Phil Stone <lists@...>

Hello,

12 messages 2012/05/27

[#396010] does this leak more than the size of the string via timing side channels — rooby shoez <lists@...>

string1 = "string"

16 messages 2012/05/29

[#396038] Is it possible to avoid longjmp in exceptions, Thread#kill, exit(), signals? — Iñaki Baz Castillo <ibc@...>

Hi, my Ruby C extension runs a C loop (libuv) without GVL. At some

8 messages 2012/05/29

Re: looking for a ruby idiom : r=foo; return r if r

From: Robert Klemme <shortcutter@...>
Date: 2012-05-24 09:30:49 UTC
List: ruby-talk #395891
On Thu, May 24, 2012 at 7:30 AM, Llelan D. <lists@ruby-forum.com> wrote:
> botp wrote in post #1061908:
>> return r if (r=3Dfoo)
>>
>> but ruby complains w(ith) undefined r
>
> This is a BUG!

No.  Local variables are defined from the location of their first
assignment.  Since the assignment comes _lexically_ after the test the
variable is undefined in the expression.  That's actually a pretty
well known property of the language - albeit a bit tricky at times.

> The expression after an IF does not define new scope, you're still in
> the containing scope. This means the initial statement of the
> if-modifier is validating the scope of any local variables before the
> if-modifier expression is evaluated.
>
> According to the "Ruby Standardization WG Draft August 25, 2010"
> Section 12.3 The if modifier statement
> Page 107
> ---------
> Semantics
> =A0An if-modifier-statement of the form S if E, where S is the statement
> and E is the expression,
> =A0is evaluated as follows:
> =A0 =A0a) Evaluate the if-expression of the form if E then S end.
> =A0 =A0b) The value of the if-modifier-statement is the resulting value.
> ---------
>
> The Semantics section item 'a' clearly states that the if-modifier
> should be interpreted in the same manner as the equivalent single-line
> if-expression. This means that the initial statement should not be
> validating local variables until after the modifier expression is
> evaluated, possibly initializing new local variables for use in the
> initial statement.

You are missing an important detail: local variable definition is done
at _parse time_.  It is purely syntactical and has nothing to do with
runtime evaluation.  What you call "validation of local variables" at
runtime does not exist.

> Please report this as an interpretor bug.

Please don't.

We're lucky because there is another idiom which fits the bill (I
won't go into lengthy explanations why I still consider assignments in
conditionals bad and only reasonable in loops):

r =3D foo and return r

Hint: different precedence of "and" compared to "&&" makes this
possible without the brackets that Matthew hat to use.

Kind regards

robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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