Improve usability of lengthCompare

[joroKr21]

In most codebases I've seen people just use seq.length/size <> n even though seq.lengthCompare(n) <> 0 is recommended for sequential collections. In some cases it's probably for lack of knowledge, but in others the latter is just deemed too unreadable.

My suggestion is to add some shortcuts that make it more pleasant to use.
Something along those lines:

def lengthEq(n: Int):  Boolean = lengthCompare(n) == 0
def lengthMin(n: Int): Boolean = lengthCompare(n) >= 0
def lengthMax(n: Int): Boolean = lengthCompare(n) <= 0

Other suggestions also welcome, of course.

This particular issue came up on Gitter.

[joroKr21]

Link to chat: https://gitter.im/scala/collection-strawman?at=5a55f0fcd0514c785b120ece

[SethTisue]

maybe lengthIs, lengthAtLeast, lengthAtMost

[sjrd]

length_==, length_>=, length_<=

[jtjeferreira]

what about adding seq.lengthCompare(anotherSeq): Int

[isaias-b]

What about this kind of interface?

implicit class SeqLikeOps[+A, +Repr](s: SeqLike[A, Repr]) {
  object lazyLength {
    def <(value:  Int) = s.lengthCompare(value) < 0
    def >(value:  Int) = s.lengthCompare(value) > 0
    def ==(value:  Int) = s.lengthCompare(value) == 0
    def <=(value:  Int) = s.lengthCompare(value) <= 0
    def >=(value:  Int) = s.lengthCompare(value) >= 0
  }
}

That allows to use:

val s: Seq[String] = ???
s.lazyLength < 10
s.lazyLength == 10
s.lazyLength > 10

However, i am not a DSL expert maybe this can be implemented without an extra inner object?

[isaias-b]

Oh is this suggestion doing the exact kind of thing? 😅 #338 (comment)

[joroKr21]

No, but the usability is almost the same (modulo _)

Oh is this suggestion doing the exact kind of thing? sweat_smile #338 (comment)

[aleks-sidorenko]

lengthEquals, lengthMoreThan, lengthLessThan