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@jashkenas
Created February 10, 2012 16:29
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# Apart from the basic niceties of being able to leave off
# parens in clear calls...
print 10
alert "Hello #{name}"
# ... the reason why they're important to have in CoffeeScript
# is because it allows our "block" syntax (single function body
# passed as the final argument to a call) to play nicely with
# significant whitespace:
fs.readFile "config/options.json", (err, contents) ->
... work with file here.
# Writing the above without the ability to leave off the
# parens which would otherwise have to wrap the function body
# would defeat a large part of the purpose of significant
# whitespace in the first place.
@jashkenas
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In my Ruby example, I'm pointing out that Ruby has to have a special case for the syntax we're talking about here, one which doesn't behave consistently with passing a function expression as an argument... We can talk about the same Ruby inconsistencies with other block forms:

puts(if true
  5
else 
  10
end)

# => 5

puts if true
  5
else 
  10
end

# => syntax error, unexpected kELSE, expecting $end

Whereas in CoffeeScript:

console.log( if true
  5
else
  10
)

# => 5

console.log if true
  5
else
  10

# => 5

... but in any case, to answer your question -- if you value visual consistency for that call, I'd recommend either of these two options:

callback = (e) ->
  ... code ...

$('some_selector).click(callback)

# Or:

$('some_selector).click( (e) ->
  ... code ...
)

... both of which work fine.

@avdi
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avdi commented Feb 10, 2012

If you don't like the HEREDOC-inspired syntax (understandable; that form of HEREDOC wigs a lot of people out), how about this. An alternate method-call syntax with very low binding priority. I'll use .. for the sake of example:

$ 'some_selector' .. click (e) ->
  ...click handler...

@avdi
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avdi commented Feb 10, 2012

The latter of your two examples is what I used, but I share your distaste for the trailing paren in a language that tries to avoid them. The former is obvious but not really helpful, since I'm looking for syntactical fixes, not code restructurings. What do you think of a low-precedence method calling syntax for chaining without parens?

@jashkenas
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Ah, interesting. An explicit "close" operator that ends implicit calls, without having to start them... That would be great material for a Github ticket, if you feel like writing it up and starting discussion. I also don't think it's something we've ever talked about before (a true rarity for CoffeeScript syntax proposals).

@avdi
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avdi commented Feb 10, 2012

@jrus
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jrus commented Feb 12, 2012

Another way to avoid the inconsistency is of course:

($ 'some selector').click (e) ->
    ...

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