From: Robert Klemme <shortcutter@...>
Date: 2011-03-08T19:17:54+09:00
Subject: Re: %s[ I think %s[] should build an array of symbols instead of a single symbol ]

On Sat, Mar 5, 2011 at 11:33 AM, Joey Zhou <yimutang@gmail.com> wrote:
> I find %s[] builds a single symbol.
>
> p %s[ I think this should build an array of symbols ]
> => :" I think this should build an array of symbols "
>
> It even costs one more keystroke than :"", so it has no effect to make
> fingers happy. If the purpose of %s[] is to avoid quotation mark
> confusion, I think %q[].to_sym is enough, and more flexible: %Q[].to_sym
> works too (well, there's no %S[]).
>
> what = "an array of symbols"
> p %Q[ I think this should build #{what} ].to_sym
> p %q[ I think this should build an array of symbols ].to_sym
>
> If I want an array of symbols, I can use %w[].map {|x| x.to_sym}:

Or even

irb(main):004:0> %w[ I think this should build an array of symbols
].map &:to_sym
=> [:I, :think, :this, :should, :build, :an, :array, :of, :symbols]

> But I think .map {|x| x.to_sym} is more expensive than .to_sym, because
> .map changes so many elements while .to_sym only changes a single
> object.

I am not sure what you mean by that.  The code with #map uses #to_sym
in a loop so both are involved.  On the other hand %s... does not use
to_sym at all I believe.

Also, expensiveness only matters if you execute the code really
frequently.  An Array of Symbols sounds like something one would
create once and store it in a class constant for example - so no need
to worry about efficiency here.

> And I think the demand for an array of symbols is more frequent
> than a single sentence-like symbol.

But the demand for Symbols containing whitespace and other special
characters might be even higher than the demand for an Array of
Symbols.

> Maybe %s[] should be changed, like %w[], not %q[]. Anyone think so?

Maybe, I don't.

Cheers

robert

-- 
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