Anonymous function syntax

[Andrei Alexandrescu]

On 9/21/11 5:17 PM, Walter Bright wrote:
> I've collected a few from various languages for comparison:
[snip]

I think we should do the following:

1. Introduce a new token "=>"

2. Add this rewrite to the grammar:

symbol => expression

translates to

(symbol) { return expression; }

3. Add this rewrite to the grammar:

symbol1 symbol2 => expression

translates to

(symbol1 symbol2) { return expression; }

4. Add this rewrite to the grammar:

(comma_separated_parms) => expression

translates to

(comma_separated_parms) => expression

Each item in comma_separated_parms may be 1 or 2 symbols separated by 
whitespace. Example:

(int a, b) => a + b

is valid and translates to (int a, b) { return a + b; }

5. The expression cannot contain commas at top level; an unparenthesized 
comma is considered to finish expression, just like in a function call's 
argument list. For example:

fun(int a => a + 1, a + 2)

is interpreted as

fun((int a => a + 1), (a + 2))

To use comma inside expression, add parens around it.

5. Remove bugs and limitations. A function literal may specify none, 
all, or some parameter types, and the compiler correctly figures out the 
appropriate template and non-template parameters. The literal 
subsequently converts to function pointer or delegate whenever there's a 
match of parameter and result types.



Andrei