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Simplify and improve Erase and EraseAll #8033

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Merged
RazvanN7 merged 1 commit into from
Aug 27, 2021
Merged

Simplify and improve Erase and EraseAll #8033

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91 changes: 18 additions & 73 deletions std/meta.d
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Original file line number Diff line number Diff line change
Expand Up @@ -302,18 +302,17 @@ if (args.length >= 1)
}

/**
* Returns an `AliasSeq` created from TList with the first occurrence,
* if any, of T removed.
* Returns an `AliasSeq` created from `args[1 .. $]` with the first occurrence,
* if any, of `args[0]` removed.
*/
template Erase(T, TList...)
{
alias Erase = GenericErase!(T, TList).result;
}

/// Ditto
template Erase(alias T, TList...)
template Erase(args...)
if (args.length >= 1)
{
alias Erase = GenericErase!(T, TList).result;
private enum pos = staticIndexOf!(args[0], args[1 .. $]);
static if (pos < 0)
alias Erase = args[1 .. $];
else
alias Erase = AliasSeq!(args[1 .. pos + 1], args[pos + 2 .. $]);
}

///
Expand All @@ -324,29 +323,6 @@ template Erase(alias T, TList...)
static assert(is(TL == AliasSeq!(int, double, char)));
}

// [internal]
private template GenericErase(args...)
if (args.length >= 1)
{
alias e = OldAlias!(args[0]);
alias tuple = args[1 .. $] ;

static if (tuple.length)
{
alias head = OldAlias!(tuple[0]);
alias tail = tuple[1 .. $];

static if (isSame!(e, head))
alias result = tail;
else
alias result = AliasSeq!(head, GenericErase!(e, tail).result);
}
else
{
alias result = AliasSeq!();
}
}

@safe unittest
{
static assert(Pack!(Erase!(int,
Expand All @@ -360,54 +336,23 @@ if (args.length >= 1)


/**
* Returns an `AliasSeq` created from TList with the all occurrences,
* if any, of T removed.
* Returns an `AliasSeq` created from `args[1 .. $]` with all occurrences,
* if any, of `args[0]` removed.
*/
template EraseAll(T, TList...)
{
alias EraseAll = GenericEraseAll!(T, TList).result;
}

/// Ditto
template EraseAll(alias T, TList...)
template EraseAll(args...)
if (args.length >= 1)
{
alias EraseAll = GenericEraseAll!(T, TList).result;
alias EraseAll = AliasSeq!();
static foreach (arg; args[1 .. $])
static if (!isSame!(args[0], arg))
EraseAll = AliasSeq!(EraseAll, arg);
}

///
@safe unittest
{
alias Types = AliasSeq!(int, long, long, int);

alias TL = EraseAll!(long, Types);
static assert(is(TL == AliasSeq!(int, int)));
}

// [internal]
private template GenericEraseAll(args...)
if (args.length >= 1)
{
alias e = OldAlias!(args[0]);
alias tuple = args[1 .. $];

static if (tuple.length)
{
alias head = OldAlias!(tuple[0]);
alias tail = tuple[1 .. $];
alias next = AliasSeq!(
GenericEraseAll!(e, tail[0..$/2]).result,
GenericEraseAll!(e, tail[$/2..$]).result
);

static if (isSame!(e, head))
alias result = next;
else
alias result = AliasSeq!(head, next);
}
else
{
alias result = AliasSeq!();
}
static assert(is(EraseAll!(long, Types) == AliasSeq!(int, int)));
}

@safe unittest
Expand Down