Programming languages should have a tree traversal primitive

blog.tylerglaiel.com

12 points by TylerGlaiel 8 months ago · 2 comments

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This is interesting, but the syntax doesn't seem to have the right expressiveness for such a large change.

    for recursive (Node t = tree.root; t != NULL;) {
      puts(t.value);
      if (t.value == target) break;
      if (t.value == dontfollow) continue;
      if (t.left) continue t.left;
      if (t.right) continue t.right;
      }
    return t;

Regular 'break' is to really break out of the structure like a regular for, as regular 'continue' is to do the next iteration. But if continue has a value to recurse on, it reenters the for loop like a subroutine.

As a bonus, I think this is tail-call-optimization friendly.

quuxplusone 8 months ago

Your zero-argument "continue" is Tyler's "prune", I think. At first glance I agree that something like your one-argument "continue" would also be helpful — like, "recurse but only down these k of the n possible child branches." That seems hard to find syntax for, unless you build the list of children ad-hoc as you go and then do "N : children)" in your increment step.

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Programming languages should have a tree traversal primitive

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