On Wednesday, 11 April 2012 at 09:43:27 UTC, Timon Gehr wrote:
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; }));
}
Better but with error ;-)
$ gdmd-4.6 func2.d
func2.d:10: Error: undefined identifier a
func2.d:10: Error: undefined identifier b
func2.d:10: Error: function func2.someprocedure (int a, int b,
int delegate(int, int) f) is not callable using argument types
(int,int,_error_ delegate(_error_, _error_))
func2.d:10: Error: cannot implicitly convert expression
(__dgliteral1) of type _error_ delegate(_error_, _error_) to int
delegate(int, int)
With:
import std.stdio;
int someprocedure (int a, int b, int delegate (int, int) f)
{
return f(a, b);
}
void main ()
{
writeln("add: ", someprocedure(2, 3, (a, b) { return a + b; }
));
writeln("multiply: ", someprocedure(2, 3, (a, b) { return a *
b; } ));
}
What is the error?
