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Merged
andralex merged 5 commits into from
Aug 15, 2018
Merged

Make each capable of early stopping #5268

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662acd4
Make each capable of early stopping
andralex Mar 12, 2017
b803ffa
It's Yes...
andralex Mar 12, 2017
8ef426d
More doc fixes
andralex Mar 12, 2017
e1d3720
Fix early stopping PR
wilzbach Aug 14, 2018
6ef73fb
Another merge
wilzbach Aug 15, 2018
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168 changes: 122 additions & 46 deletions std/algorithm/iteration.d
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Original file line number Diff line number Diff line change
Expand Up @@ -849,32 +849,40 @@ private struct MapResult(alias fun, Range)

// each
/**
Eagerly iterates over `r` and calls `pred` over _each element.
Eagerly iterates over `r` and calls `fun` over _each element.

If no predicate is specified, `each` will default to doing nothing
but consuming the entire range. `.front` will be evaluated, but this
can be avoided by explicitly specifying a predicate lambda with a
`lazy` parameter.
If no function to call is specified, `each` defaults to doing nothing but
consuming the entire range. `r.front` will be evaluated, but that can be avoided
by specifying a lambda with a `lazy` parameter.

`each` also supports `opApply`-based iterators, so it will work
with e.g. $(REF parallel, std,parallelism).
`each` also supports `opApply`-based types, so it works with e.g. $(REF
parallel, std,parallelism).

Normally the entire range is iterated. If partial iteration (early stopping) is
desired, `fun` needs to return a value of type $(REF Flag,
std.typecons)`!"each"` (`Yes.each` to continue iteration, or `No.each` to stop
iteration).

Params:
pred = predicate to apply to each element of the range
r = range or iterable over which each iterates
fun = function to apply to _each element of the range
r = range or iterable over which `each` iterates

Returns: `Yes.each` if the entire range was iterated, `No.each` in case of early
stopping.

See_Also: $(REF tee, std,range)
*/
template each(alias pred = "a")
template each(alias fun = "a")
{
import std.meta : AliasSeq;
import std.traits : Parameters;
import std.typecons : Flag, Yes, No;

private:
alias BinaryArgs = AliasSeq!(pred, "i", "a");
alias BinaryArgs = AliasSeq!(fun, "i", "a");

enum isRangeUnaryIterable(R) =
is(typeof(unaryFun!pred(R.init.front)));
is(typeof(unaryFun!fun(R.init.front)));

enum isRangeBinaryIterable(R) =
is(typeof(binaryFun!BinaryArgs(0, R.init.front)));
Expand All @@ -886,19 +894,19 @@ private:
enum isForeachUnaryIterable(R) =
is(typeof((R r) {
foreach (ref a; r)
cast(void) unaryFun!pred(a);
cast(void) unaryFun!fun(a);
}));

enum isForeachUnaryWithIndexIterable(R) =
is(typeof((R r) {
foreach (i, ref a; r)
cast(void) unaryFun!pred(i, a);
cast(void) binaryFun!BinaryArgs(i, a);
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@wilzbach wilzbach Aug 15, 2018

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This was incorrect.

}));

enum isForeachBinaryIterable(R) =
is(typeof((R r) {
foreach (ref a, ref b; r)
cast(void) binaryFun!BinaryArgs(a, b);
cast(void) binaryFun!fun(a, b);
}));

enum isForeachIterable(R) =
Expand All @@ -911,7 +919,7 @@ public:
Params:
r = range or iterable over which each iterates
*/
void each(Range)(Range r)
Flag!"each" each(Range)(Range r)
if (!isForeachIterable!Range && (
isRangeIterable!Range ||
__traits(compiles, typeof(r.front).length)))
Expand All @@ -923,7 +931,15 @@ public:
{
while (!r.empty)
{
cast(void) unaryFun!pred(r.front);
static if (!is(typeof(unaryFun!fun(r.front)) == Flag!"each"))
{
cast(void) unaryFun!fun(r.front);
}
else
{
if (unaryFun!fun(r.front) == No.each) return No.each;
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@wilzbach wilzbach Aug 15, 2018

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The braces are required to avoid DScanner's "Mismatched static if. Use 'else static if' here." warning.

}

r.popFront();
}
}
Expand All @@ -932,7 +948,14 @@ public:
size_t i = 0;
while (!r.empty)
{
cast(void) binaryFun!BinaryArgs(i, r.front);
static if (!is(typeof(binaryFun!BinaryArgs(i, r.front)) == Flag!"each"))
{
cast(void) binaryFun!BinaryArgs(i, r.front);
}
else
{
if (binaryFun!BinaryArgs(i, r.front) == No.each) return No.each;
}
r.popFront();
i++;
}
Expand All @@ -942,50 +965,100 @@ public:
{
// range interface with >2 parameters.
for (auto range = r; !range.empty; range.popFront())
pred(range.front.expand);
{
static if (!is(typeof(fun(r.front.expand)) == Flag!"each"))
{
cast(void) fun(range.front.expand);
}
else
{
if (fun(range.front.expand)) return No.each;
}
}
}
return Yes.each;
}

/**
Params:
r = range or iterable over which each iterates
*/
void each(Iterable)(auto ref Iterable r)
/// ditto
Flag!"each" each(Iterable)(auto ref Iterable r)
if (isForeachIterable!Iterable ||
__traits(compiles, Parameters!(Parameters!(r.opApply))))
{
static if (isForeachIterable!Iterable)
{
debug(each) pragma(msg, "Using foreach for ", Iterable.stringof);
static if (isForeachUnaryIterable!Iterable)
{
foreach (ref e; r)
cast(void) unaryFun!pred(e);
debug(each) pragma(msg, "Using foreach UNARY for ", Iterable.stringof);
{
foreach (ref e; r)
{
static if (!is(typeof(unaryFun!fun(e)) == Flag!"each"))
{
cast(void) unaryFun!fun(e);
}
else
{
if (unaryFun!fun(e) == No.each) return No.each;
}
}
}
}
else static if (isForeachBinaryIterable!Iterable)
{
foreach (ref a, ref b; r)
cast(void) binaryFun!BinaryArgs(a, b);
}
else static if (isForeachUnaryWithIndexIterable!Iterable)
{
foreach (i, ref e; r)
cast(void) binaryFun!BinaryArgs(i, e);
else static if (isForeachBinaryIterable!Iterable)
{
debug(each) pragma(msg, "Using foreach BINARY for ", Iterable.stringof);
foreach (ref a, ref b; r)
{
static if (!is(typeof(binaryFun!fun(a, b)) == Flag!"each"))
{
cast(void) binaryFun!fun(a, b);
}
else
{
if (binaryFun!fun(a, b) == No.each) return No.each;
}
}
}
else
{
static assert(0, "An impossible static if branch was reached");
}
else static if (isForeachUnaryWithIndexIterable!Iterable)
{
debug(each) pragma(msg, "Using foreach INDEX for ", Iterable.stringof);
foreach (i, ref e; r)
{
static if (!is(typeof(binaryFun!BinaryArgs(i, e)) == Flag!"each"))
{
cast(void) binaryFun!BinaryArgs(i, e);
}
else
{
if (binaryFun!BinaryArgs(i, e) == No.each) return No.each;
}
}
}
else
{
static assert(0, "Invalid foreach iteratable type " ~ Iterable.stringof ~ " met.");
}
return Yes.each;
}
else
{
// opApply with >2 parameters. count the delegate args.
// only works if it is not templated (otherwise we cannot count the args)
auto dg(Parameters!(Parameters!(r.opApply)) params) {
pred(params);
return 0; // tells opApply to continue iteration
auto result = Yes.each;
auto dg(Parameters!(Parameters!(r.opApply)) params)
{
static if (!is(typeof(binaryFun!BinaryArgs(i, e)) == Flag!"each"))
{
fun(params);
return 0; // tells opApply to continue iteration
}
else
{
result = fun(params);
return result == Yes.each ? 0 : -1;
}
}
r.opApply(&dg);
return result;
}
}
}
Expand All @@ -994,17 +1067,20 @@ public:
@system unittest
{
import std.range : iota;
import std.typecons : Flag, Yes, No;

long[] arr;
iota(5).each!(n => arr ~= n);
assert(arr == [0, 1, 2, 3, 4]);
iota(5).each!((n) { arr ~= n; return No.each; });
assert(arr == [0, 1, 2, 3, 4, 0]);

// If the range supports it, the value can be mutated in place
arr.each!((ref n) => n++);
assert(arr == [1, 2, 3, 4, 5]);
assert(arr == [1, 2, 3, 4, 5, 1]);

arr.each!"a++";
assert(arr == [2, 3, 4, 5, 6]);
assert(arr == [2, 3, 4, 5, 6, 2]);

// by-ref lambdas are not allowed for non-ref ranges
static assert(!is(typeof(arr.map!(n => n).each!((ref n) => n++))));
Expand All @@ -1017,7 +1093,7 @@ public:
// Indexes are also available for in-place mutations
arr[] = 0;
arr.each!"a=i"();
assert(arr == [0, 1, 2, 3, 4]);
assert(arr == [0, 1, 2, 3, 4, 5]);

// opApply iterators work as well
static class S
Expand Down