Is ternary operator meant to use lazy evaluation?

[mdmcconnell]

I had some expressions of the form "false ? do_something() : do_otherthing()", and it seems as though do_something() was always called. Before I spend much time working up a test - is ternary operator even meant to use lazy evaluation?

[antonmedv]

Yes! Ternary operator designed to be short circuiting.

If you need to run both expressions, assign the to variables. And use ternary operator on them.

[mdmcconnell]

Strange - The behaviour I observed indicates the opposite. Maybe it is application-specific; must run a few tests. I'll revert if I find anything interesting.

[mdmcconnell]

Ah, my problem will be because I am overriding ternary operator with a patcher like this:

	case *ast.ConditionalNode:
		callNode := &ast.CallNode{
			Callee:    &ast.IdentifierNode{Value: "ternOverride"},
			Arguments: []ast.Node{n.Cond, n.Exp1, n.Exp2},
		}
		ast.Patch(node, callNode)

So it is no longer operating with the normal behaviour.

[antonmedv]

Yes, in this case, it is a call. To perform a call we need to know all the arguments.

[mdmcconnell]

For the sake of some future coder who discovers this thread - one solution is to insert a new node in the tree that checks the condition first, then uses a ConditionalNode on the outcome of that condition. And check that the ConditionalNode in question hasn't already been patched - to avoid infinite patching.