[tests] basic min/max test cases

[frootloops]

No description provided.

[gribozavr]

@frootloops Thank you! We have some basic tests in validation-test/stdlib/Algorithm.swift, could you consolidate these?

Also, could you rewrite the tests using MinimalComparableValue and check the identity of the object being returned? The identity will be arbitrary (not following any useful rule) now, but it is important to constrain it. If you feel like doing library code changes, you could implement what we discussed in pull request #137 that would make the identity useful:

On a preordered set, the argument goes, min of two equivalent elements should return the first parameter, and max should return the second.

[frootloops]

@gribozavr can you have a look through the PR. I rewrite max<T : Comparable>(x: T, _ y: T, _ z: T, _ rest: T...) -> T and I need your code review because I suspect it may be slower than the previous version.

Thank you for MinimalComparableValue it makes writing test more easier.

[gribozavr]

You don't need to have separate value and identity tests. All value tests could just check identity as well.

[frootloops]

@gribozavr done

[gribozavr]

You are still creating an array here, this will be slow.

[frootloops]

@gribozavr what do you think about next code:

public func max<T : Comparable>(x: T, _ y: T, _ z: T, _ rest: T...) -> T {
  var r = max(max(x, y), z)
  for t in rest where t >= r {
    r = t
  }
  return r
}

or do you prefer a classic way:

public func max<T : Comparable>(x: T, _ y: T, _ z: T, _ rest: T...) -> T {
  var r = x
  if y >= r {
    r = y
  }
  if z >= r {
    r = z
  }
  for t in rest where t >= r {
    r = t
  }
  return r
}

[gribozavr]

@frootloops As long as it would be possible to implement the idea discussed in #137, I'm ok with the short one.

[frootloops]

@gribozavr please have a look. I hope it's all right.

[gribozavr]

@frootloops Looks great, thanks! From the tests we see that we already implement #137.