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Implement moveFront, moveBack, moveAt

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... and hasMobileElements.
This commit is contained in:
Eugen Wissner 2018-03-22 10:44:58 +01:00
parent 7829b1fe06
commit a7c1e642e9
1 changed files with 499 additions and 0 deletions
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499
source/tanya/range/primitive.d
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@ -14,6 +14,7 @@
*/
module tanya.range.primitive;
import tanya.algorithm.mutation;
import tanya.math;
import tanya.meta.trait;
import tanya.meta.transform;
@ -1355,3 +1356,501 @@ if (isBidirectionalRange!R)
assert(range.empty);
}
}
/**
* Moves the front element of an input range.
*
* The front element is left in a valid but inspecified state.
* $(D_PSYMBOL moveFront) doesn't advances the range, so `popFront` should be
* probably called after this function.
*
* Params:
* R = Type of the range.
* range = Input range.
*
* Returns: The front element of the $(D_PSYMBOL range).
*
* See_Also: $(D_PSYMBOL move).
*/
ElementType!R moveFront(R)(R range)
if (isInputRange!R)
{
static if (is(typeof(R.moveFront)))
{
return range.moveFront();
}
else static if (!hasElaborateCopyConstructor!(ElementType!R))
{
return range.front;
}
else static if (is(typeof(((ref ElementType!R e) => e)(range.front))))
{
return move(range.front);
}
else
{
static assert(false, "Front element cannot be moved");
}
}
///
@nogc nothrow pure @safe unittest
{
// Defines moveFront.
static struct R1
{
enum bool empty = false;
int moveFront() @nogc nothrow pure @safe
{
return 5;
}
alias front = moveFront;
void popFront() @nogc nothrow pure @safe
{
}
}
assert(moveFront(R1()) == 5);
// Has elements without a postblit constructor.
static struct R2
{
enum bool empty = false;
int front() const @nogc nothrow pure @safe
{
return 5;
}
void popFront() @nogc nothrow pure @safe
{
}
}
assert(moveFront(R2()) == 5);
static struct Element
{
this(this)
{
assert(false);
}
}
// Returns its elements by reference.
static struct R3
{
Element element;
enum bool empty = false;
ref Element front() @nogc nothrow pure @safe
{
return element;
}
void popFront() @nogc nothrow pure @safe
{
}
}
static assert(is(typeof(moveFront(R3()))));
// Returns elements with a postblit constructor by value. moveFront fails.
static struct R4
{
enum bool empty = false;
Element front() @nogc nothrow pure @safe
{
return Element();
}
void popFront() @nogc nothrow pure @safe
{
}
}
static assert(!is(typeof(moveFront(R4()))));
}
/**
* Moves the back element of a bidirectional range.
*
* The back element is left in a valid but inspecified state.
* $(D_PSYMBOL moveBack) doesn't advances the range, so `popBack` should be
* probably called after this function.
*
* Params:
* R = Type of the range.
* range = Bidirectional range.
*
* Returns: The back element of the $(D_PSYMBOL range).
*
* See_Also: $(D_PSYMBOL move).
*/
ElementType!R moveBack(R)(R range)
if (isBidirectionalRange!R)
{
static if (is(typeof(R.moveBack)))
{
return range.moveBack();
}
else static if (!hasElaborateCopyConstructor!(ElementType!R))
{
return range.back;
}
else static if (is(typeof(((ref ElementType!R e) => e)(range.back))))
{
return move(range.back);
}
else
{
static assert(false, "Back element cannot be moved");
}
}
///
@nogc nothrow pure @safe unittest
{
// Defines moveBack.
static struct R1
{
enum bool empty = false;
int moveBack() @nogc nothrow pure @safe
{
return 5;
}
alias back = moveBack;
alias front = moveBack;
void popBack() @nogc nothrow pure @safe
{
}
alias popFront = popBack;
R1 save() @nogc nothrow pure @safe
{
return this;
}
}
assert(moveBack(R1()) == 5);
// Has elements without a postblit constructor.
static struct R2
{
enum bool empty = false;
int back() const @nogc nothrow pure @safe
{
return 5;
}
alias front = back;
void popBack() @nogc nothrow pure @safe
{
}
alias popFront = popBack;
R2 save() @nogc nothrow pure @safe
{
return this;
}
}
assert(moveBack(R2()) == 5);
static struct Element
{
this(this)
{
assert(false);
}
}
// Returns its elements by reference.
static struct R3
{
Element element;
enum bool empty = false;
ref Element back() @nogc nothrow pure @safe
{
return element;
}
alias front = back;
void popBack() @nogc nothrow pure @safe
{
}
alias popFront = popBack;
R3 save() @nogc nothrow pure @safe
{
return this;
}
}
static assert(is(typeof(moveBack(R3()))));
// Returns elements with a postblit constructor by value. moveBack fails.
static struct R4
{
enum bool empty = false;
Element back() @nogc nothrow pure @safe
{
return Element();
}
alias front = back;
void popBack() @nogc nothrow pure @safe
{
}
alias popFront = popBack;
R4 save() @nogc nothrow pure @safe
{
return this;
}
}
static assert(!is(typeof(moveBack(R4()))));
}
/**
* Moves the element at the position $(D_PARAM n) out of the range.
*
* The moved element is left in a valid but inspecified state.
*
* Params:
* R = Type of the range.
* range = Random-access range.
* n = Element position.
*
* Returns: The element at the position $(D_PARAM n).
*
* See_Also: $(D_PSYMBOL move).
*/
ElementType!R moveAt(R)(R range, size_t n)
if (isRandomAccessRange!R)
{
static if (is(typeof(R.moveAt)))
{
return range.moveAt(n);
}
else static if (!hasElaborateCopyConstructor!(ElementType!R))
{
return range[n];
}
else static if (is(typeof(((ref ElementType!R e) => e)(range[0]))))
{
return move(range[n]);
}
else
{
static assert(false, "Back element cannot be moved");
}
}
///
@nogc nothrow pure @safe unittest
{
// Defines moveAt.
static struct R1
{
enum bool empty = false;
int front() @nogc nothrow pure @safe
{
return 5;
}
void popFront() @nogc nothrow pure @safe
{
}
int moveAt(size_t) @nogc nothrow pure @safe
{
return 5;
}
alias opIndex = moveAt;
}
assert(moveAt(R1(), 0) == 5);
// Has elements without a postblit constructor.
static struct R2
{
enum bool empty = false;
int front() const @nogc nothrow pure @safe
{
return 5;
}
void popFront() @nogc nothrow pure @safe
{
}
int opIndex(size_t) const @nogc nothrow pure @safe
{
return 5;
}
}
assert(moveAt(R2(), 0) == 5);
static struct Element
{
this(this)
{
assert(false);
}
}
// Returns its elements by reference.
static struct R3
{
Element element;
enum bool empty = false;
ref Element front() @nogc nothrow pure @safe
{
return element;
}
void popFront() @nogc nothrow pure @safe
{
}
ref Element opIndex(size_t)
{
return element;
}
}
static assert(is(typeof(moveAt(R3(), 0))));
// Returns elements with a postblit constructor by value. moveAt fails.
static struct R4
{
enum bool empty = false;
Element front() @nogc nothrow pure @safe
{
return Element();
}
void popFront() @nogc nothrow pure @safe
{
}
Element opIndex() @nogc nothrow pure @safe
{
return Element();
}
}
static assert(!is(typeof(moveAt(R4(), 0))));
}
/**
* Determines whether $(D_PSYMBOL R) is a range containing mobile elements,
* i.e. elements that can be moved out of the range.
*
* Having mobile elements means for an input range to support
* $(D_PSYMBOL moveFront), for a bidirectional range - both,
* $(D_PSYMBOL moveFront) and $(D_PSYMBOL moveBack), for a random-access -
* $(D_PSYMBOL moveFront) and $(D_PSYMBOL moveAt).
*
* Params:
* R = Range type.
*
* Returns: $(D_KEYWORD true) if $(D_PSYMBOL R) has mobile elements,
* $(D_KEYWORD false) otherwise.
*
* See_Also: $(D_PSYMBOL moveFront), $(D_PSYMBOL moveBack),
* $(D_PSYMBOL moveAt).
*/
template hasMobileElements(R)
{
static if (isRandomAccessRange!R)
{
enum bool hasMobileElements = is(typeof((R r) => moveFront(r)))
&& is(typeof((R r) => moveAt(r, 0)));
}
else static if (isBidirectionalRange!R)
{
enum bool hasMobileElements = is(typeof((R r) => moveFront(r)))
&& is(typeof((R r) => moveBack(r)));
}
else
{
enum bool hasMobileElements = is(typeof((R r) => moveFront(r)));
}
}
///
@nogc nothrow pure @safe unittest
{
// Input range with elements without a postblit constructor.
// These can be moved.
static struct InputRange
{
enum bool empty = false;
int front() @nogc nothrow pure @safe
{
return 5;
}
void popFront() @nogc nothrow pure @safe
{
}
}
static assert(hasMobileElements!InputRange);
static struct Element
{
this(this)
{
}
}
// Bidirectional range, whose elements cannot be moved. The range defines
// only moveFront, but not moveBack. So it doesn't have mobile elements.
static struct BidirectionalRange
{
enum bool empty = false;
Element front() @nogc nothrow pure @safe
{
return Element();
}
alias back = front;
alias moveFront = front;
void popFront() @nogc nothrow pure @safe
{
}
alias popBack = popFront;
BidirectionalRange save() @nogc nothrow pure @safe
{
return this;
}
}
static assert(!hasMobileElements!BidirectionalRange);
// Access-random range, whose elements cannot be moved, but the range
// defines both, moveFront and moveAt.
static struct RandomAccessRange
{
enum bool empty = false;
Element front() @nogc nothrow pure @safe
{
return Element();
}
alias moveFront = front;
void popFront() @nogc nothrow pure @safe
{
}
Element opIndex(size_t) @nogc nothrow pure @safe
{
return Element();
}
alias moveAt = opIndex;
}
static assert(hasMobileElements!RandomAccessRange);
}