Julia: High Performance Programming

Map, filter, and list comprehensions

Maps and filters are typical for functional languages. A map is a function of the form map(func, coll), where func is a (often anonymous) function that is successively applied to every element of the coll collection, so map returns a new collection. Some examples are as follows:

• map(x -> x * 10, [1, 2, 3]) returns [10, 20, 30]
• cubes = map(x-> x^3, [1:5]) returns [1, 8, 27, 64, 125]

Map can also be used with functions that take more than one argument. In this case, it requires a collection for each argument, for example, map(*, [1, 2, 3], [4, 5, 6]) works per element and returns [4, 10, 18].

When the function passed to map requires several lines, it can be a bit unwieldy to write this as an anonymous function. For ...