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Merge pull request #3288 from nordlow/struct-returned-findSplit
Struct Returned findSplit*() with implicit bool conversion
This commit is contained in:
Andrei Alexandrescu
commit
b6a61d9e71
2 changed files with 117 additions and 37 deletions
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@ -2404,20 +2404,49 @@ Params:
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needle = What to look for.
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Returns:
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A tuple of the split portions of `haystack` (see above for details).
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A sub-type of Tuple!() of the split portions of `haystack` (see above for
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details). This sub-type of Tuple!() has opCast defined for bool. This opCast
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returns $(D true) when the separating $(D needle) was found (!result[1].empty)
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and $(D false) otherwise. This enables the convenient idiom shown in the
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following example.
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Example:
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---
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if (const split = haystack.findSplit(needle))
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{
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doSomethingWithSplit(split);
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}
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---
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*/
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auto findSplit(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
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if (isForwardRange!R1 && isForwardRange!R2)
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{
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static struct Result(S1, S2) if (isForwardRange!S1 &&
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isForwardRange!S2)
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{
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this(S1 pre, S1 separator, S2 post)
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{
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asTuple = typeof(asTuple)(pre, separator, post);
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}
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Tuple!(S1, S1, S2) asTuple;
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bool opCast(T : bool)()
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{
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return !asTuple[1].empty;
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}
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alias asTuple this;
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}
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static if (isSomeString!R1 && isSomeString!R2
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|| isRandomAccessRange!R1 && hasLength!R2)
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{
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auto balance = find!pred(haystack, needle);
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immutable pos1 = haystack.length - balance.length;
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immutable pos2 = balance.empty ? pos1 : pos1 + needle.length;
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return tuple(haystack[0 .. pos1],
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haystack[pos1 .. pos2],
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haystack[pos2 .. haystack.length]);
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return Result!(typeof(haystack[0 .. pos1]),
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typeof(haystack[pos2 .. haystack.length]))(haystack[0 .. pos1],
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haystack[pos1 .. pos2],
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haystack[pos2 .. haystack.length]);
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}
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else
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{
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@ -2442,9 +2471,10 @@ if (isForwardRange!R1 && isForwardRange!R2)
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pos2 = ++pos1;
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}
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}
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return tuple(takeExactly(original, pos1),
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takeExactly(haystack, pos2 - pos1),
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h);
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return Result!(typeof(takeExactly(original, pos1)),
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typeof(h))(takeExactly(original, pos1),
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takeExactly(haystack, pos2 - pos1),
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h);
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}
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}
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@ -2452,12 +2482,29 @@ if (isForwardRange!R1 && isForwardRange!R2)
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auto findSplitBefore(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
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if (isForwardRange!R1 && isForwardRange!R2)
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{
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static struct Result(S1, S2) if (isForwardRange!S1 &&
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isForwardRange!S2)
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{
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this(S1 pre, S2 post)
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{
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asTuple = typeof(asTuple)(pre, post);
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}
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Tuple!(S1, S2) asTuple;
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bool opCast(T : bool)()
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{
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return !asTuple[0].empty;
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}
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alias asTuple this;
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}
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static if (isSomeString!R1 && isSomeString!R2
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|| isRandomAccessRange!R1 && hasLength!R2)
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{
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auto balance = find!pred(haystack, needle);
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immutable pos = haystack.length - balance.length;
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return tuple(haystack[0 .. pos], haystack[pos .. haystack.length]);
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return Result!(typeof(haystack[0 .. pos]),
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typeof(haystack[pos .. haystack.length]))(haystack[0 .. pos],
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haystack[pos .. haystack.length]);
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}
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else
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{
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@ -2481,7 +2528,9 @@ if (isForwardRange!R1 && isForwardRange!R2)
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++pos;
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}
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}
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return tuple(takeExactly(original, pos), haystack);
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return Result!(typeof(takeExactly(original, pos)),
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typeof(haystack))(takeExactly(original, pos),
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haystack);
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}
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}
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@ -2489,12 +2538,29 @@ if (isForwardRange!R1 && isForwardRange!R2)
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auto findSplitAfter(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
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if (isForwardRange!R1 && isForwardRange!R2)
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{
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static struct Result(S1, S2) if (isForwardRange!S1 &&
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isForwardRange!S2)
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{
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this(S1 pre, S2 post)
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{
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asTuple = typeof(asTuple)(pre, post);
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}
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Tuple!(S1, S2) asTuple;
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bool opCast(T : bool)()
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{
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return !asTuple[1].empty;
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}
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alias asTuple this;
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}
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static if (isSomeString!R1 && isSomeString!R2
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|| isRandomAccessRange!R1 && hasLength!R2)
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{
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auto balance = find!pred(haystack, needle);
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immutable pos = balance.empty ? 0 : haystack.length - balance.length + needle.length;
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return tuple(haystack[0 .. pos], haystack[pos .. haystack.length]);
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return Result!(typeof(haystack[0 .. pos]),
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typeof(haystack[pos .. haystack.length]))(haystack[0 .. pos],
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haystack[pos .. haystack.length]);
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}
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else
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{
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@ -2508,7 +2574,9 @@ if (isForwardRange!R1 && isForwardRange!R2)
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if (h.empty)
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{
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// Failed search
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return tuple(takeExactly(original, 0), original);
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return Result!(typeof(takeExactly(original, 0)),
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typeof(original))(takeExactly(original, 0),
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original);
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}
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if (binaryFun!pred(h.front, n.front))
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{
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@ -2524,7 +2592,9 @@ if (isForwardRange!R1 && isForwardRange!R2)
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pos2 = ++pos1;
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}
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}
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return tuple(takeExactly(original, pos2), h);
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return Result!(typeof(takeExactly(original, pos2)),
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typeof(h))(takeExactly(original, pos2),
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h);
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}
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}
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@ -2533,6 +2603,10 @@ if (isForwardRange!R1 && isForwardRange!R2)
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{
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auto a = "Carl Sagan Memorial Station";
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auto r = findSplit(a, "Velikovsky");
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import std.typecons : isTuple;
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static assert(isTuple!(typeof(r.asTuple)));
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static assert(isTuple!(typeof(r)));
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assert(!r);
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assert(r[0] == a);
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assert(r[1].empty);
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assert(r[2].empty);
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@ -2541,9 +2615,11 @@ if (isForwardRange!R1 && isForwardRange!R2)
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assert(r[1] == " ");
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assert(r[2] == "Sagan Memorial Station");
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auto r1 = findSplitBefore(a, "Sagan");
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assert(r1);
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assert(r1[0] == "Carl ", r1[0]);
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assert(r1[1] == "Sagan Memorial Station");
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auto r2 = findSplitAfter(a, "Sagan");
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assert(r2);
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assert(r2[0] == "Carl Sagan");
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assert(r2[1] == " Memorial Station");
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}
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@ -2552,27 +2628,33 @@ if (isForwardRange!R1 && isForwardRange!R2)
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{
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auto a = [ 1, 2, 3, 4, 5, 6, 7, 8 ];
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auto r = findSplit(a, [9, 1]);
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assert(!r);
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assert(r[0] == a);
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assert(r[1].empty);
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assert(r[2].empty);
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r = findSplit(a, [3]);
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assert(r);
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assert(r[0] == a[0 .. 2]);
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assert(r[1] == a[2 .. 3]);
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assert(r[2] == a[3 .. $]);
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auto r1 = findSplitBefore(a, [9, 1]);
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assert(r1);
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assert(r1[0] == a);
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assert(r1[1].empty);
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r1 = findSplitBefore(a, [3, 4]);
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assert(r1);
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assert(r1[0] == a[0 .. 2]);
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assert(r1[1] == a[2 .. $]);
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r1 = findSplitAfter(a, [9, 1]);
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assert(r1[0].empty);
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assert(r1[1] == a);
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r1 = findSplitAfter(a, [3, 4]);
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assert(r1[0] == a[0 .. 4]);
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assert(r1[1] == a[4 .. $]);
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auto r2 = findSplitAfter(a, [9, 1]);
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assert(r2);
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assert(r2[0].empty);
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assert(r2[1] == a);
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r2 = findSplitAfter(a, [3, 4]);
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assert(r2);
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assert(r2[0] == a[0 .. 4]);
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assert(r2[1] == a[4 .. $]);
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}
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@safe unittest
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@ -2583,27 +2665,33 @@ if (isForwardRange!R1 && isForwardRange!R2)
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auto a = [ 1, 2, 3, 4, 5, 6, 7, 8 ];
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auto fwd = filter!"a > 0"(a);
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auto r = findSplit(fwd, [9, 1]);
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assert(!r);
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assert(equal(r[0], a));
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assert(r[1].empty);
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assert(r[2].empty);
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r = findSplit(fwd, [3]);
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assert(r);
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assert(equal(r[0], a[0 .. 2]));
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assert(equal(r[1], a[2 .. 3]));
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assert(equal(r[2], a[3 .. $]));
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auto r1 = findSplitBefore(fwd, [9, 1]);
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assert(r1);
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assert(equal(r1[0], a));
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assert(r1[1].empty);
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r1 = findSplitBefore(fwd, [3, 4]);
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assert(r1);
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assert(equal(r1[0], a[0 .. 2]));
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assert(equal(r1[1], a[2 .. $]));
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r1 = findSplitAfter(fwd, [9, 1]);
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assert(r1[0].empty);
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assert(equal(r1[1], a));
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r1 = findSplitAfter(fwd, [3, 4]);
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assert(equal(r1[0], a[0 .. 4]));
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assert(equal(r1[1], a[4 .. $]));
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auto r2 = findSplitAfter(fwd, [9, 1]);
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assert(r2);
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assert(r2[0].empty);
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assert(equal(r2[1], a));
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r2 = findSplitAfter(fwd, [3, 4]);
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assert(r2);
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assert(equal(r2[0], a[0 .. 4]));
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assert(equal(r2[1], a[4 .. $]));
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}
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/**
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@ -3528,4 +3616,3 @@ unittest // Issue 13124
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auto s = "hello how\nare you";
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s.until!(c => c.among!('\n', '\r'));
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}
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