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Improve AliasSeq Map example

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Inline simple functions, move testRef next to where it's used.
This commit is contained in:
Nick Treleaven 2020-06-09 18:29:41 +01:00
parent 6d6e04bf6a
commit 74416ab6eb
1 changed files with 20 additions and 40 deletions
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60
std/meta.d
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@ -110,70 +110,50 @@ alias AliasSeq(TList...) = TList;
}
/**
Returns an `AliasSeq` expression of `Func` being
applied to every variadic template argument.
*/
///
@safe unittest
{
auto ref ArgCall(alias Func, alias arg)()
// Creates a compile-time sequence of function call expressions
// that each call `func` with the next variadic template argument
template Map(alias func, args...)
{
return Func(arg);
}
alias lazyItem = function auto ref() => func(args[0]);
template Map(alias Func, args...)
{
static if (args.length > 1)
static if (args.length == 1)
{
alias Map = AliasSeq!(ArgCall!(Func, args[0]), Map!(Func, args[1 .. $]));
alias Map = lazyItem;
}
else
{
alias Map = ArgCall!(Func, args[0]);
// recurse
alias Map = AliasSeq!(lazyItem, Map!(func, args[1 .. $]));
}
}
static int square(int arg)
{
return arg * arg;
}
static int refSquare(ref int arg)
{
arg *= arg;
return arg;
}
static ref int refRetSquare(ref int arg)
{
arg *= arg;
return arg;
}
static void test(int a, int b)
{
assert(a == 4);
assert(b == 16);
}
static int a = 2;
static int b = 4;
test(Map!(i => i ^^ 2, a, b));
assert(a == 2);
assert(b == 4);
test(Map!((ref i) => i *= i, a, b));
assert(a == 4);
assert(b == 16);
static void testRef(ref int a, ref int b)
{
assert(a++ == 16);
assert(b++ == 256);
}
static int a = 2;
static int b = 4;
test(Map!(square, a, b));
test(Map!(refSquare, a, b));
assert(a == 4);
assert(b == 16);
testRef(Map!(refRetSquare, a, b));
testRef(Map!(function ref(ref i) => i *= i, a, b));
assert(a == 17);
assert(b == 257);
}