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Comment by openbear | Hacker News Reader

I'm glad to see these additions, but the syntax for an NSArray literal bugs me.

When I want an array literal in C, I'd write ...

  int foo[] = { 1, 2, 3, 4, 5};

... but in Objective-C, for an NSArray literal I'd write ...

  NSArray *bar = @[o1, o2, o3];

Why did they choose '[' over '{'? Oddly enough, NSDictionary uses '{'.

I feel like the syntax for an NSString literal is more natural (as a C developer).

  NSString *baz = @"look, an NSString literal";
  char szBaz[] = "look, a C string literal";

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Because presumably (I don't have the new XCode to check) you can do things like:

    [someObject dictArg:@{ a:@"B" } arrayArg:@[1,2,34]];

So if they were both using "{" to set them off the parser doesn't know which one you mean until it hits the first ":" (and it can't guess from the type when the type is "id"). Now that's not impossible to write a parser that looks ahead to figure out what you mean, but it's much easier to parse if they have completely different syntax from the outset. And the "{" vs "[" distinction is very standard amongst the higher level languages, even if it isn't in straight C.

I think they chose the [] for arrays and {} for dictionaries as that is the style that seems to be most popular right now. Python for instance uses this.

And Perl. And Javascript. And Ruby. There's lots of precedent.

When adding features to something, I tend to be a big fan of "when in Rome"[1]. If these were extensions to Python (or Ruby or JavaScript) then I would totally be for using '[' with arrays. As a C guy though, I would rather have seen them use '{' for NSArray and '[' for NSDictionary. Regardless, I'm glad to see this stuff added.

[1] http://en.wiktionary.org/wiki/when_in_Rome,_do_as_the_Romans...

It's already custom in objc to use {} for dicts and [] for arrays when printing them out, unless I'm misremembering. It also matches the use of those characters in JSON, so it seems natural to me.

Could be in case they want to do literal NSValues later. Since {}-syntax is used in C for both array literals and struct literals, they needed to change one, and the picked the more common one. Otherwise is foo in:

id foo = @{ @2, @5 };

an NSArray containing two NSNumbers, or an NSValue containing a struct with two pointers (which happen to be NSNumber *s)?

I'd guess there were other edge cases they didn't want to deal with, so they didn't do literal NSValues for this release.

Or it could be that it's because []-style arrays are popular these days.

Or some of both; in picking which {} to change to @[], they reasoned that lots of people have experience with []-style arrays.

> Why did they choose '[' over '{'? Oddly enough, NSDictionary uses '{'.

Who knows, but it seems to mirror Python in that respect. Being a fan of Python I can only approve.

Completely agree. Looks natural to me as a python/javascript guy

Perhaps they choose @[ for arrays because it requires less lookahead than figuring out whether @{ is the start of a dictionary or an array.

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