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Merge pull request #7632 from andralex/minmax

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Simplify min and max
This commit is contained in:
Andrei Alexandrescu 2020-09-19 16:19:07 -04:00 • committed by GitHub
commit 311f00f8ac
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1 changed files with 50 additions and 76 deletions
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126
std/algorithm/comparison.d
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@ -1129,29 +1129,6 @@ range of range (of range...) comparisons.
assert(!"bar".equal(E()));
}
// MaxType
private template MaxType(T...)
if (T.length >= 1)
{
static if (T.length == 1)
{
alias MaxType = T[0];
}
else static if (T.length == 2)
{
static if (!is(typeof(T[0].min)))
alias MaxType = CommonType!T;
else static if (T[1].max > T[0].max)
alias MaxType = T[1];
else
alias MaxType = T[0];
}
else
{
alias MaxType = MaxType!(MaxType!(T[0 .. ($+1)/2]), MaxType!(T[($+1)/2 .. $]));
}
}
// levenshteinDistance
/**
Encodes $(HTTP realityinteractive.com/rgrzywinski/archives/000249.html,
@ -1561,31 +1538,40 @@ Returns:
See_Also:
$(REF maxElement, std,algorithm,searching)
*/
MaxType!T max(T...)(T args)
if (T.length >= 2)
auto max(T...)(T args)
if (T.length >= 2 && !is(CommonType!T == void))
{
//Get "a"
static if (T.length <= 2)
// Get left-hand side of the comparison.
static if (T.length == 2)
alias a = args[0];
else
auto a = max(args[0 .. ($+1)/2]);
auto a = max(args[0 .. ($ + 1) / 2]);
alias T0 = typeof(a);
//Get "b"
// Get right-hand side.
static if (T.length <= 3)
alias b = args[$-1];
alias b = args[$ - 1];
else
auto b = max(args[($+1)/2 .. $]);
auto b = max(args[($ + 1) / 2 .. $]);
alias T1 = typeof(b);
static assert(is(typeof(a < b)),
"Invalid arguments: Cannot compare types " ~ T0.stringof ~
" and " ~ T1.stringof ~ ".");
" and " ~ T1.stringof ~ " for ordering.");
//Do the "max" proper with a and b
// Compute the returned type.
static if (is(typeof(mostNegative!T0 < mostNegative!T1)))
// Both are numeric (or character or Boolean), so we choose the one with the highest maximum.
// (We use mostNegative for num/bool/char testing purposes even if it's not used otherwise.)
alias Result = Select!(T1.max > T0.max, T1, T0);
else
// At least one is non-numeric, so just go with the common type.
alias Result = CommonType!(T0, T1);
// Perform the computation.
import std.functional : lessThan;
immutable chooseB = lessThan!(T0, T1)(a, b);
return cast(typeof(return)) (chooseB ? b : a);
return cast(Result) (chooseB ? b : a);
}
///
@ -1631,38 +1617,6 @@ if (T.length >= 2)
assert(max(Date.max, Date.min) == Date.max);
}
// MinType
private template MinType(T...)
if (T.length >= 1)
{
static if (T.length == 1)
{
alias MinType = T[0];
}
else static if (T.length == 2)
{
static if (!is(typeof(T[0].min)))
alias MinType = CommonType!T;
else
{
enum hasMostNegative = is(typeof(mostNegative!(T[0]))) &&
is(typeof(mostNegative!(T[1])));
static if (hasMostNegative && mostNegative!(T[1]) < mostNegative!(T[0]))
alias MinType = T[1];
else static if (hasMostNegative && mostNegative!(T[1]) > mostNegative!(T[0]))
alias MinType = T[0];
else static if (T[1].max < T[0].max)
alias MinType = T[1];
else
alias MinType = T[0];
}
}
else
{
alias MinType = MinType!(MinType!(T[0 .. ($+1)/2]), MinType!(T[($+1)/2 .. $]));
}
}
// min
/**
Iterates the passed arguments and returns the minimum value.
@ -1681,31 +1635,43 @@ Returns:
See_Also:
$(REF minElement, std,algorithm,searching)
*/
MinType!T min(T...)(T args)
if (T.length >= 2)
auto min(T...)(T args)
if (T.length >= 2 && !is(CommonType!T == void))
{
//Get "a"
// Get the left-hand side of the comparison.
static if (T.length <= 2)
alias a = args[0];
else
auto a = min(args[0 .. ($+1)/2]);
auto a = min(args[0 .. ($ + 1) / 2]);
alias T0 = typeof(a);
//Get "b"
// Get the right-hand side.
static if (T.length <= 3)
alias b = args[$-1];
alias b = args[$ - 1];
else
auto b = min(args[($+1)/2 .. $]);
auto b = min(args[($ + 1) / 2 .. $]);
alias T1 = typeof(b);
static assert(is(typeof(a < b)),
"Invalid arguments: Cannot compare types " ~ T0.stringof ~
" and " ~ T1.stringof ~ ".");
" and " ~ T1.stringof ~ " for ordering.");
//Do the "min" proper with a and b
// Compute the returned type.
static if (is(typeof(mostNegative!T0 < mostNegative!T1)))
// Both are numeric (or character or Boolean), so we choose the one with the lowest minimum.
// If they have the same minimum, choose the one with the smallest size.
// If both mostNegative and sizeof are equal, go for stability: pick the type of the first one.
alias Result = Select!(mostNegative!T1 < mostNegative!T0 ||
mostNegative!T1 == mostNegative!T0 && T1.sizeof < T0.sizeof,
T1, T0);
else
// At least one is non-numeric, so just go with the common type.
alias Result = CommonType!(T0, T1);
// Engage!
import std.functional : lessThan;
immutable chooseB = lessThan!(T1, T0)(b, a);
return cast(typeof(return)) (chooseB ? b : a);
return cast(Result) (chooseB ? b : a);
}
///
@ -1720,6 +1686,14 @@ if (T.length >= 2)
auto e = min(a, b, c);
static assert(is(typeof(e) == double));
assert(e == 2);
ulong f = 0xffff_ffff_ffff;
const uint g = min(f, 0xffff_0000);
assert(g == 0xffff_0000);
dchar h = 100;
uint i = 101;
static assert(is(typeof(min(h, i)) == dchar));
static assert(is(typeof(min(i, h)) == uint));
assert(min(h, i) == 100);
}
/**