Higher-order functions?

[Timon Gehr]

On 04/11/2012 11:37 AM, Xan wrote:
> On Wednesday, 11 April 2012 at 09:17:12 UTC, Jacob Carlborg wrote:
>> On 2012-04-11 10:45, Xan wrote:
>>> Good answer.
>>>
>>> For the other hand, what is the simplest method for implementing this
>>> (in pseucode) in D:
>>>
>>> Sure:
>>>
>>> FUNC someprocedure(int a, int b, func<int, int: int> f) int
>>> RETURN f(a, b)
>>> }
>>>
>>> And call it with:
>>>
>>> IO.writeLine("add: " .. someprocedure(2, 3, { a, b => a + b }))
>>> IO.writeLine("multiply: " .. someprocedure(2, 3, { a, b => a * b }))
>>>
>>> (Read the => as "gives")
>>>
>>> Is it possible to have this?
>>>
>>
>> If I understand the above code correctly:
>>
>> import std.stdio;
>>
>> int someprocedure (int a, int b, int delegate (int, int) f)
>> {
>>     return f(a, b);
>> }
>>
>
>
> Yes, you undertood correcty.
>
> Your code gives me an error:
>
> $ gdmd-4.6 funcions.d
> funcions.d:10: expression expected, not '>'
> funcions.d:10: found 'a' when expecting ','
> funcions.d:11: expression expected, not '>'
> funcions.d:11: found 'a' when expecting ','
>
>> void main ()
>> {
>>     writeln("add: ", someprocedure(2, 3, (a, b) => a + b));
>>     writeln("multiply: ", someprocedure(2, 3, (a, b) => a * b));
>> }
>
>

AFAIK GDC does not yet support the new lambda literal syntax.

You can use

void main ()
{
     writeln("add: ", someprocedure(2, 3, (a, b) { return a + b; }));
     writeln("multiply: ", someprocedure(2, 3, (a, b) { return a * b; }));
}