io.atlassian.fugue.law

Class SemigroupLaws<A>

java.lang.Object

io.atlassian.fugue.law.SemigroupLaws<A>

public final class SemigroupLaws<A>
extends Object

Laws for a semigroup

Constructor Summary

Constructors

Constructor and Description
SemigroupLaws(Semigroup<A> semigroup) Build a law instance to check semigroup properties

Method Summary

Modifier and Type	Method and Description
IsEq<A>	multiply1pEqualRepeatedAppend(int n, A a) The Semigroup.multiply1p(int, Object) function of your semigroup must be equal to Semigroup.sumNonEmpty(Object, Iterable) applied to the input and an iterable containing n - 1 copies of that input
IsEq<A>	semigroupAssociative(A x, A y, A z) A semigroup must not care about the order elements are combined.
IsEq<A>	sumNonEmptyEqualFold(A head, Iterable<A> tail) The Semigroup.sumNonEmpty(Object, Iterable) function of your semigroup must be equal to a Functions.fold(BiFunction, Object, Iterable) where append is used as the combining function, head is used as the initial value and tail is the iterable to check

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SemigroupLaws

public SemigroupLaws(Semigroup<A> semigroup)

Build a law instance to check semigroup properties

Parameters:

semigroup - a Semigroup to check matches the desired behaviors of

Method Detail

semigroupAssociative

public IsEq<A> semigroupAssociative(A x,
                                    A y,
                                    A z)

A semigroup must not care about the order elements are combined. If you combine x with y and then with z the result should be the same as combining y with z and then with x.

Parameters:

x - an A object

y - an A object

z - an A object

Returns:

a IsEq instance where append(append(x,y),z) is equal to append(x, append(y,z))

sumNonEmptyEqualFold

public IsEq<A> sumNonEmptyEqualFold(A head,
                                    Iterable<A> tail)

The Semigroup.sumNonEmpty(Object, Iterable) function of your semigroup must be equal to a Functions.fold(BiFunction, Object, Iterable) where append is used as the combining function, head is used as the initial value and tail is the iterable to check

Parameters:

head - an A

tail - a Iterable of A's

Returns:

a IsEq where sumeNonEmpty(head, tail) is equal to fold(append, head, tail)

multiply1pEqualRepeatedAppend

public IsEq<A> multiply1pEqualRepeatedAppend(int n,
                                             A a)

The Semigroup.multiply1p(int, Object) function of your semigroup must be equal to Semigroup.sumNonEmpty(Object, Iterable) applied to the input and an iterable containing n - 1 copies of that input

Parameters:

n - a int representing the number of copies of the input to combine

a - an A

Returns:

a IsEq where multiply(n,a) is equal to sumNonEmpty(a, take(n-1, cycle(a))