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findSplit, findSplitBefore, findSplitAfter

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This commit is contained in:
Andrei Alexandrescu 2011-01-23 15:44:03 +00:00
parent 2fb2876d67
commit c84f8a6a56
1 changed files with 160 additions and 16 deletions
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176
std/algorithm.d
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@ -2989,7 +2989,7 @@ bool findSkip(alias pred = "a == b", R1, R2)(ref R1 haystack, R2 needle)
if (isForwardRange!R1 && isForwardRange!R2
&& is(typeof(binaryFun!pred(haystack.front, needle.front))))
{
auto parts = findParts!pred(haystack, needle);
auto parts = findSplit!pred(haystack, needle);
if (parts[1].empty) return false;
// found
haystack = parts[2];
@ -3007,12 +3007,30 @@ unittest
}
/**
Given a $(D haystack) and a $(D needle), returns a tuple $(D result)
containing three ranges: $(D result[0]) is the portion of $(D
haystack) before $(D needle), $(D result[1]) is the portion of $(D
haystack) that matches $(D needle), and $(D result[2]) is the portion
of $(D haystack) after the match.
These functions find the first occurrence of $(D needle) in $(D
haystack) and then split $(D haystack) as follows.
$(D findSplit) returns a tuple $(D result) containing $(I three)
ranges. $(D result[0]) is the portion of $(D haystack) before $(D
needle), $(D result[1]) is the portion of $(D haystack) that matches
$(D needle), and $(D result[2]) is the portion of $(D haystack) after
the match.
$(D findSplitBefore) returns a tuple $(D result) containing two
ranges. $(D result[0]) is the portion of $(D haystack) before $(D
needle), and $(D result[1]) is the balance of $(D haystack) starting
with the match. If $(D needle) was not found, $(D result[0])
comprehends $(D haystack) entirely and $(D result[1]) is empty.
$(D findSplitAfter) returns a tuple $(D result) containing two ranges.
$(D result[0]) is the portion of $(D haystack) up to and including the
match, and $(D result[1]) is the balance of $(D haystack) starting
after the match. If $(D needle) was not found, $(D result[0]) is empty
and $(D result[1]) is $(D haystack).
In all cases, the concatenation of the returned ranges spans the
entire $(D haystack).
If $(D haystack) is a random-access range, all three components of the
tuple have the same type as $(D haystack). Otherwise, $(D haystack)
must be a forward range and the type of $(D result[0]) and $(D
@ -3021,17 +3039,23 @@ result[1]) is the same as $(XREF range,takeExactly).
Example:
----
auto a = [ 1, 2, 3, 4, 5, 6, 7, 8 ];
auto r = findParts(a, [9, 1]);
auto r = findSplit(a, [9, 1]);
assert(r[0] == a);
assert(r[1].empty);
assert(r[2].empty);
r = findParts(a, [3]);
r = findSplit(a, [ 3, 4 ]);
assert(r[0] == a[0 .. 2]);
assert(r[1] == a[2 .. 3]);
assert(r[2] == a[3 .. $]);
assert(r[1] == a[2 .. 4]);
assert(r[2] == a[4 .. $]);
auto r1 = findSplitBefore(a, [ 7, 8 ]);
assert(r1[0] == a[0 .. 6]);
assert(r1[1] == a[6 .. $]);
auto r1 = findSplitAfter(a, [ 7, 8 ]);
assert(r1[0] == a);
assert(r1[1].empty);
----
*/
auto findParts(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
auto findSplit(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
if (isForwardRange!R1 && isForwardRange!R2)
{
static if (isSomeString!R1 && isSomeString!R2
@ -3039,7 +3063,7 @@ if (isForwardRange!R1 && isForwardRange!R2)
{
auto balance = find!pred(haystack, needle);
immutable pos1 = haystack.length - balance.length;
immutable pos2 = balance.length ? pos1 + needle.length : pos1;
immutable pos2 = balance.empty ? pos1 : pos1 + needle.length;
return tuple(haystack[0 .. pos1],
haystack[pos1 .. pos2],
haystack[pos2 .. haystack.length]);
@ -3067,22 +3091,142 @@ if (isForwardRange!R1 && isForwardRange!R2)
}
}
return tuple(takeExactly(original, pos1),
takeExactly(haystack, pos2),
takeExactly(haystack, pos2 - pos1),
h);
}
}
/// Ditto
auto findSplitBefore(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
if (isForwardRange!R1 && isForwardRange!R2)
{
static if (isSomeString!R1 && isSomeString!R2
|| isRandomAccessRange!R1 && hasLength!R2)
{
auto balance = find!pred(haystack, needle);
immutable pos = haystack.length - balance.length;
return tuple(haystack[0 .. pos], haystack[pos .. haystack.length]);
}
else
{
auto original = haystack.save;
auto h = haystack.save;
auto n = needle.save;
size_t pos;
while (!n.empty && !h.empty)
{
if (binaryFun!pred(h.front, n.front))
{
h.popFront();
n.popFront();
}
else
{
haystack.popFront();
n = needle.save;
h = haystack.save;
++pos;
}
}
return tuple(takeExactly(original, pos), haystack);
}
}
/// Ditto
auto findSplitAfter(alias pred = "a == b", R1, R2)(R1 haystack, R2 needle)
if (isForwardRange!R1 && isForwardRange!R2)
{
static if (isSomeString!R1 && isSomeString!R2
|| isRandomAccessRange!R1 && hasLength!R2)
{
auto balance = find!pred(haystack, needle);
immutable pos = balance.empty ? 0 : haystack.length - balance.length + needle.length;
return tuple(haystack[0 .. pos], haystack[pos .. haystack.length]);
}
else
{
auto original = haystack.save;
auto h = haystack.save;
auto n = needle.save;
size_t pos1, pos2;
while (!n.empty)
{
if (h.empty)
{
// Failed search
return tuple(takeExactly(original, 0), original);
}
if (binaryFun!pred(h.front, n.front))
{
h.popFront();
n.popFront();
++pos2;
}
else
{
haystack.popFront();
n = needle.save;
h = haystack.save;
pos2 = ++pos1;
}
}
return tuple(takeExactly(original, pos2), h);
}
}
unittest
{
auto a = [ 1, 2, 3, 4, 5, 6, 7, 8 ];
auto r = findParts(a, [9, 1]);
assert(equal(r[0], a));
auto r = findSplit(a, [9, 1]);
assert(r[0] == a);
assert(r[1].empty);
assert(r[2].empty);
r = findParts(a, [3]);
r = findSplit(a, [3]);
assert(r[0] == a[0 .. 2]);
assert(r[1] == a[2 .. 3]);
assert(r[2] == a[3 .. $]);
auto r1 = findSplitBefore(a, [9, 1]);
assert(r1[0] == a);
assert(r1[1].empty);
r1 = findSplitBefore(a, [3, 4]);
assert(r1[0] == a[0 .. 2]);
assert(r1[1] == a[2 .. $]);
r1 = findSplitAfter(a, [9, 1]);
assert(r1[0].empty);
assert(r1[1] == a);
r1 = findSplitAfter(a, [3, 4]);
assert(r1[0] == a[0 .. 4]);
assert(r1[1] == a[4 .. $]);
}
unittest
{
auto a = [ 1, 2, 3, 4, 5, 6, 7, 8 ];
auto fwd = filter!"a > 0"(a);
auto r = findSplit(fwd, [9, 1]);
assert(equal(r[0], a));
assert(r[1].empty);
assert(r[2].empty);
r = findSplit(fwd, [3]);
assert(equal(r[0], a[0 .. 2]));
assert(equal(r[1], a[2 .. 3]));
assert(equal(r[2], a[3 .. $]));
auto r1 = findSplitBefore(fwd, [9, 1]);
assert(equal(r1[0], a));
assert(r1[1].empty);
r1 = findSplitBefore(fwd, [3, 4]);
assert(equal(r1[0], a[0 .. 2]));
assert(equal(r1[1], a[2 .. $]));
r1 = findSplitAfter(fwd, [9, 1]);
assert(r1[0].empty);
assert(equal(r1[1], a));
r1 = findSplitAfter(fwd, [3, 4]);
assert(equal(r1[0], a[0 .. 4]));
assert(equal(r1[1], a[4 .. $]));
}
/**