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Function std.functional.toDelegate

Convert a callable to a delegate with the same parameter list and return type, avoiding heap allocations and use of auxiliary storage.

auto toDelegate(F) (
  auto ref F fp
)
if (isCallable!F);

Parameters

NameDescription
fp a function pointer or an aggregate type with opCall defined.

Returns

A delegate with the context pointer pointing to nothing.

Example

void doStuff() {
    writeln("Hello, world.");
}

void runDelegate(void delegate() myDelegate) {
    myDelegate();
}

auto delegateToPass = toDelegate(&doStuff);
runDelegate(delegateToPass);  // Calls doStuff, prints "Hello, world."

BUGS

  • Does not work with @safe functions.
  • Ignores C-style / D-style variadic arguments.

Example

static int inc(ref uint num) {
    num++;
    return 8675309;
}

uint myNum = 0;
auto incMyNumDel = toDelegate(&inc);
auto returnVal = incMyNumDel(myNum);
writeln(myNum); // 1

Authors

Andrei Alexandrescu

License

Boost License 1.0.