ginger/functions.md

Functions

Functions are first-class citizens in ginger. The simplest anonymous function can be created like so:

(. fn [x]
    (: + x 1))

This function takes in a single number and returns that number plus one. It could be assigned to a variable on the package using def, or by using the shortcut defn. The following two statements are equivalent:

(. def incr
    (. fn [x]
        (: + x 1)))

(. defn incr [x]
    (: + x 1))

Function returns

Single returns

A function returns whatever the last expression in its execution returned. For example:

(. defn abs [x]
    (. if (: >= x 0)
        x
        (: * -1 x)))

This function will return the argument x if it is greater than or equal to 0, or (* -1 x) if it's not.

Multiple returns

A function which wishes to return multiple arguments should return them as a vector or list of arguments. The let function, which can be used to define temporary variables in a scope, can deconstruct these multiple-returns:

# Returns two numbers which sum up to 10
(. defn sum-10 []
    [4 6])

(. let [[foo bar] (: sum-10)
    (: fmt.Println "%d + %d = 10" foo bar))

Functions defined within a go library which return multiple values can also be deconstructed in a let statement:

(. let [[conn err] (: net.Dial "tcp" "localhost:80")]
    # do stuff)

Variadic function

Functions may take in any number of variables using the ... syntax, similar to how go does variadic functions. The variadic variable must be the last in the function's argument list, and is used as a list inside of the function. A list may also be used as the input for a variadic function, also using the ... syntax.

The following is an example of both defining a variadic function and both ways of using it. + is a variadic function in this example:

(. defn avg [...x]
    (/
        (+ x...)
        (len x)))

(: fmt.Println (avg 1 2 3 4 5))