Evaluate expression/s under some condition

if[test;e1;e2;e3;…;en]

Control construct. Where

• test is an expression that evaluates to an atom of integral type
• e1, e2, … en are expressions

unless test evaluates to zero, the expressions e1 to en are evaluated, in order.

The result of if is always the generic null.

q)a:100
q)r:""
q)if[a>10;a:20;r:"true"]
q)a
20
q)r
"true"