Concatenation

{} represents bit concatenation. In {}, repeat keyword can be used to repeat specified operand.

module ModuleA {
    let a : logic<10> = 1;
    let b : logic<10> = 1;
    let _c: logic     = {a[9:0], b[4:3]};
    let _d: logic     = {a[9:0] repeat 10, b repeat 4};
}