Function calls

Simple

A distinction between PRQL and most other programming languages is the function call syntax. It consists of the function name followed by arguments separated by whitespace.

function_name arg1 arg2 arg3

If one of the arguments is also a function call, it must be encased in parentheses, so we know where arguments of inner function end and the arguments of outer function start.

outer_func arg_1 (inner_func arg_a, arg_b) arg_2

The function name must refer to a function variable, which has either been declared in the standard library or some other module.

Function calls can also specify named parameters using : notation:

function_name arg1 named_param:arg2 arg3

Pipeline

There is a alternative way of calling functions: using a pipeline. Regardless of whether the pipeline is delimited by pipe symbol | or a new line, the pipeline is equivalent to applying each of functions as the last argument of the next function.

a | foo 3 | bar 'hello' 'world' | baz

... is equivalent to ...

baz (bar 'hello' 'world' (foo 3 a))