From: dm1 <dmertz@...>
Date: 2005-04-23T21:24:31+09:00
Subject: Re: Clean way to dynamically expand string with "#{expression}"?

Taisuke Yamada wrote:

> Yes, what I was looking for is 'perfect interpolation on demand'
> that'll work whatever content is in interpolated string. I guess
> 
>    eval("<<END_REEVAL\n" + self + "\nEND_REEVAL\n", b)
> 
> is the best (and robust) solution available as you can choose
> random string that probably won't show up in interpolated string.

Ah the quest for perfection, we are still not there :

irb(main):001:0> str = "blah\nEND_REEVAL\n catch me if you can"
=> "blah\nEND_REEVAL\n catch me if you can"
irb(main):002:0> eval("<<END_REEVAL\n" + str + "\nEND_REEVAL\n", binding)
NameError: undefined local variable or method `can' for main:Object
        from (irb):5
        from (irb):2


i.e. it will fail for every string containing the "\nEND_REEVAL\n" string
delimiter. 

> 
> Many interpolation code, including mine and several people
> suggested will break if '"' or certain string is contained
> in string to interpolate.
> 
> Practically, it doesn't need to be perfect, but it was my
> technical interest that there may be better way to do it.
> Above code is cleaner and more robust, so I'll go with it.
> Thanks for the pointer.
> 

I do share that technical interest. I really wonder if there is a one liner
for 'perfect interpolation on demand'. Everything i can think of is a bit
longer. Let the quest continue :)

Ciao

Denis