Triadic ? (vector conditional)

This verb returns value made of second or third argument depending on first boolean scalar or vector argument. Think about vector if-then-else expression. Boolean truth results in second argument usage, false - in third one.

First scalar boolean is the same condition expression.

o)?[1b;1;2]
1
o)?[0b;0 1 2;2 2 3]
2 2 3
o)

First vector boolean is much more useful. Second and third argument should have compatible types. All arguments must have the same shape.

o)?[011b;2 2 3;1 1 1]
1 2 3
o)?[001b;1;(2;"123";3)]
2
"123"
1
o)