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[std.range.chain] Use static assert instead of complex constraint #8821

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[std.range.chain] Use static assert instead of complex constraint #8821

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[std.range.chain] Use static assert instead of complex constraint
ntrel Sep 22, 2023
53afc45
Avoid `static if`
ntrel Sep 22, 2023
5934c38
Similar for choose and chooseAmong
ntrel Sep 22, 2023
f75118b
Require >=1 input range in constraint for consistency
ntrel Nov 6, 2023
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35 changes: 25 additions & 10 deletions std/range/package.d
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Original file line number Diff line number Diff line change
Expand Up @@ -928,9 +928,17 @@ See_Also: $(LREF only) to chain values to a range
*/
auto chain(Ranges...)(Ranges rs)
if (Ranges.length > 0 &&
allSatisfy!(isInputRange, staticMap!(Unqual, Ranges)) &&
!is(CommonType!(staticMap!(ElementType, staticMap!(Unqual, Ranges))) == void))
anySatisfy!(isInputRange, staticMap!(Unqual, Ranges)))
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Is there a reason to have this anySatisfy constraint here but not on chooseAmong?

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I've added this constraint to chooseAmong now for consistency. The only reason was I thought that was a less likely name to have a collision (see my next comment).

{
alias R = staticMap!(Unqual, Ranges);
static foreach (T; R)
{
static assert(isInputRange!T, "`", T, "` is not an input range");
}
alias RvalueElementType = CommonType!(staticMap!(ElementType, R));
static assert(!is(RvalueElementType == void),
"No common element type for ranges `", Ranges, "`");

static if (Ranges.length == 1)
{
return rs[0];
Expand All @@ -940,8 +948,6 @@ if (Ranges.length > 0 &&
static struct Result
{
private:
alias R = staticMap!(Unqual, Ranges);
alias RvalueElementType = CommonType!(staticMap!(.ElementType, R));
template sameET(A)
{
enum sameET = is(.ElementType!A == RvalueElementType);
Expand Down Expand Up @@ -1722,9 +1728,11 @@ Returns:
A range type dependent on `R1` and `R2`.
*/
auto choose(R1, R2)(bool condition, return scope R1 r1, return scope R2 r2)
if (isInputRange!(Unqual!R1) && isInputRange!(Unqual!R2) &&
!is(CommonType!(ElementType!(Unqual!R1), ElementType!(Unqual!R2)) == void))
if (isInputRange!(Unqual!R1) && isInputRange!(Unqual!R2))
{
static assert(!is(CommonType!(ElementType!(Unqual!R1), ElementType!(Unqual!R2)) == void),
"No common element type for `", R1, "` and `", R2, "`");

size_t choice = condition? 0: 1;
return ChooseResult!(R1, R2)(choice, r1, r2);
}
Expand Down Expand Up @@ -2170,11 +2178,18 @@ Returns:
alias of that range's type.
*/
auto chooseAmong(Ranges...)(size_t index, return scope Ranges rs)
if (Ranges.length >= 2
&& allSatisfy!(isInputRange, staticMap!(Unqual, Ranges))
&& !is(CommonType!(staticMap!(ElementType, Ranges)) == void))
if (Ranges.length >= 2 &&
anySatisfy!(isInputRange, staticMap!(Unqual, Ranges)))
{
return ChooseResult!Ranges(index, rs);
alias URs = staticMap!(Unqual, Ranges);
static foreach (T; URs)
{
static assert(isInputRange!T, "`", T, "` is not an input range");
}
static assert(!is(CommonType!(staticMap!(ElementType, URs)) == void),
"No common element type for `", Ranges, "`");

return ChooseResult!Ranges(index, rs);
}

///
Expand Down