WordPress at a glance
function is not described

WC_Legacy_Cart::add_discount() public WC 1.0

Renamed for consistency.

{} It's a method of the class: WC_Legacy_Cart{}

No Hooks.

Return

true/false True. if the coupon is applied, false if it does not exist or cannot be applied.

Usage

$WC_Legacy_Cart = new WC_Legacy_Cart();
$WC_Legacy_Cart->add_discount( $coupon_code );
$coupon_code(string) (required)
-

Code of WC_Legacy_Cart::add_discount() WC 5.0.0

<?php
public function add_discount( $coupon_code ) {
	return $this->apply_coupon( $coupon_code );
}