_{Official ZPE/YASS documentation}Arrow Expressions

ZPE 1.14.4 introduced arrow expressions, a new type of lambda function called a predicate lambda.

These lambda functions absolutely must return a boolean. They are clever in the sense that any function that can take them as a parameter can also set the parameters really quickly.

These are simple expressions that can be passed as a parameter to a function as shown below:

$a = [44, 32, 99]
//Will print 44
print($a.where(n => n % 2 == 0)
   

Each time the loop inside the where method runs, it will run the predicate lambda to decide if the number meets the requirements. If it's true, the element is added to the output list of the where method.

Notes

It is really important to note that predicate lambdas expect just one expression. This can include && and || but it must terminate in a single expression.