Hacker News Reader

Comment by ghayes | Hacker News Reader

I like to think of the square root of x function:

    r such that r * r = x

That’s a specification that gives you no knowledge how to solve the problem. You can definitely have precise specifications that do not directly correlate to machine instructions.

View on HN

And:

  print "Hello, World!"

gives no knowledge how to put text on the screen. Conversely, there's no reason a standard library couldn't include:

  fn (*) :: Num -> Num -> Num
  fn (a * b) = [machine code goes here]
  un (_ * d) n = n/d
  un (d * _) n = n/d
  un (_ * _) n = sqrt(n)

or similar.

Well then, "all you need to do" is convert your non constructive proof into a constructive one - et, voila :-)

I like this answer because it says it will require someone with specific knowledge and specific training doing a specific job anyway...

Also "anyway" a specification is always incomplete. It's part of the programmers' job to fill the gaps with something sensible, and when they have no idea what to do, to point out that some corner case was overlooked.

This is where programmers sometimes start to feel like Lieutenant Columbo: at first everyone is nice, but people become more and more irritated as the pesky cop asks more and more embarrassing questions.

at first everyone is nice, but people become more and more irritated as the pesky cop asks more and more embarrassing questions.

You just summed up about 20% of my job

Isn't that basically how you'd write it in Prolog?

Reply on news.ycombinator.com