From: Brian Candler <b.candler@...>
Date: 2009-12-06T19:17:24+09:00
Subject: Re: Why doesn't Ruby "compile" strings?

I単aki Baz Castillo wrote:
>> When you are using the string literals, the interpreter doesn't know what
>> you are going to do with that string literal, so it's not really safe for
>>  it to assume that it can use a single ruby object to represent all
>>  instances of it.
> 
> Why not? It's obviously a string writen in the script, with no variables 
> into
> it and so...

Suppose you do:

  10.times do
    puts "hello"
  end

The interpreter has no way of knowing that puts does not mutate the 
argument passed to it. This is a silly example, but you might have done:

  alias :old_puts :puts
  def puts(x)
    old_puts x
    x.replace "rubbish"
  end

So it is forced to create a new string object each time round the loop.

It's a shame that Ruby doesn't have immutable strings. Symbols are the 
closest, but they have different semantics to strings.

If the literal syntax "xxx" gave a *frozen* String, then it would be 
safe to re-use it. But then if you wanted to append to a string, you'd 
have to write:

  a = "".dup
  a << "stuff"

or perhaps

  a = String.new
  a << "stuff"

Regards,

Brian.
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