[Swift-devel] app syntax ambiguity

[Mihael Hategan]

On Sun, 2007-12-16 at 13:38 +0000, Ben Clifford wrote:
> Expressions have been mostly self delimiting, which is useful in the app{} 
> block syntax where there are no delimiters between the parameters of an 
> application. For example, given the input: 21*33 14*96 that can be parsed 
> as two expressions, the first one 21*33 and the second one 14*96.
> 
> The sequence of tokens for this coming out of the lexer is: 21 * 33 14 * 
> 96
> 
> There's some ambiguity when it comes to unary +/- eg 21 -33 could be 
> either a single expression (21-33) or two expressions 21 and -33.

Would we be ok (from an aesthetic/usability) perspective with commas as
separators there? Or even with representing the args as an array?

If not, then I think the unary operators should have precedence and if
the user wants to have a single expression, parentheses can be used
(e.g. (21-33) (14+16))

> 
> However, no one has commented on having trouble with this before.
> 
> Putting in multi-dimensional array support adds more ambiguity along the 
> same lines, this time interacting with array literals.
> 
> i[1][2] might mean two parameters i[1] and an array literal [2] or it 
> might mean one parameter accessing a multidimensional array i[1][2].

Or both? As in multidimensional arrays are arrays of arrays. What we
want, I'm guessing, is the possibility to easily pass i[1] as an array
parameter instead of using something like i[i, *].

> 
> Changing the syntax used to specify array literals would resolve this, as 
> would putting in specific delimiters in the app block. The former is 
> probably the least intrusive in terms of already written user scripts.
>