-
-
Notifications
You must be signed in to change notification settings - Fork 1.2k
/
UnorderedFoldableLaws.scala
85 lines (71 loc) · 3.02 KB
/
UnorderedFoldableLaws.scala
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
/*
* Copyright (c) 2015 Typelevel
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package cats
package laws
import cats.kernel.CommutativeMonoid
trait UnorderedFoldableLaws[F[_]] {
implicit def F: UnorderedFoldable[F]
def unorderedFoldConsistentWithUnorderedFoldMap[A: CommutativeMonoid](fa: F[A]): IsEq[A] =
F.unorderedFoldMap(fa)(identity) <-> F.unorderedFold(fa)
def forallConsistentWithExists[A](fa: F[A], p: A => Boolean): Boolean =
if (F.forall(fa)(p)) {
val negationExists = F.exists(fa)(a => !p(a))
// if p is true for all elements, then there cannot be an element for which
// it does not hold.
!negationExists &&
// if p is true for all elements, then either there must be no elements
// or there must exist an element for which it is true.
(F.isEmpty(fa) || F.exists(fa)(p))
} else true // can't test much in this case
def existsLazy[A](fa: F[A]): Boolean = {
var i = 0
F.exists(fa) { _ =>
i += 1
true
}
i == (if (F.isEmpty(fa)) 0 else 1)
}
def forallLazy[A](fa: F[A]): Boolean = {
var i = 0
F.forall(fa) { _ =>
i += 1
false
}
i == (if (F.isEmpty(fa)) 0 else 1)
}
/**
* If `F[A]` is empty, forall must return true.
*/
def forallEmpty[A](fa: F[A], p: A => Boolean): Boolean =
!F.isEmpty(fa) || F.forall(fa)(p)
def nonEmptyRef[A](fa: F[A]): IsEq[Boolean] =
F.nonEmpty(fa) <-> !F.isEmpty(fa)
def containsConsistentWithExists[A](fa: F[A], v: A)(implicit eq: Eq[A]): IsEq[Boolean] =
F.contains_(fa, v) <-> F.exists(fa)(a => eq.eqv(a, v))
def containsConsistentWithForall[A](fa: F[A], v: A)(implicit eq: Eq[A]): IsEq[Boolean] =
!F.contains_(fa, v) <-> F.forall(fa)(a => eq.neqv(a, v))
def containsAllElementsFromItself[A](fa: F[A])(implicit eq: Eq[A]): Boolean =
F.forall(fa)(a => F.contains_(fa, a))
}
object UnorderedFoldableLaws {
def apply[F[_]](implicit ev: UnorderedFoldable[F]): UnorderedFoldableLaws[F] =
new UnorderedFoldableLaws[F] { def F: UnorderedFoldable[F] = ev }
}