Skip to content

Functions

RSL offers a range of built-in functions to help you write your scripts. In this section, we'll take a look at the syntax and a few examples. For a complete list of available functions, see the reference.

Syntax

The syntax for invoking functions is pretty standard. Here's a script with some examples:

names = ["Bob", "Charlie", "Alice"]
num_people = len(names)
print("There are {num_people} people.")

sorted_names = sort(names)
print(sorted_names)

There are 3 people.
[Alice, Bob, Charlie]

This example uses a few different functions:

  • len
  • print
  • sort

No Arguments

Some functions take no arguments. For example, rand() returns a random float between 0 and 1:

random_float = rand()
print(random_float)

0.8436881320514183

Fixed Arguments

Some functions take a fixed number of arguments, such as upper and lower that always take one argument:

text = "oh WOW!"
print(upper(text))
print(lower(text))

OH WOW!
oh wow!

Variadic Arguments

Some functions can take different numbers of arguments! For example join:

numbers = [1, 2, 3]
print(join(numbers, "... "))

print(join(numbers, "... ", "Okay I'll count. "))

print(join(numbers, "... ", "Okay I'll count. ", "!"))

1... 2... 3
Okay I'll count. 1... 2... 3
Okay I'll count. 1... 2... 3!

In this example, join is being invoked with all these valid variations:

  • join(list, joiner)
  • join(list, joiner, prefix)
  • join(list, joiner, prefix, suffix)

Example using join for url query params

The second variation of join can be handy for generating the query params in a url. For example:

url = "https://api.github.com/repos/amterp/rad/commits"
query_params = ["per_page=5", "path=README.md"]
url += join(query_params, "&", "?")
print(url)

In this example, the final url will be the following valid URL utilizing those query params: https://api.github.com/repos/amterp/rad/commits?path=README.md&per_page=5

Named Arguments

Finally, some functions may also have named arguments. An example of this is http_post. http_post (unsurprisingly) performs an HTTP POST request against an input url, usually with a body of some sort. One variation of the function only takes that url:

response = http_post(url, body)

However, if you wish to customize the headers on your HTTP request, you can do so:

my_headers = {
    "Authorization": "Bearer {token}",
}
response = http_post(url, body, headers=my_headers)

In this example, the named arg headers expects a map. Named args are always optional. Required arguments cannot be specified as required arguments.

Reference

There are a lot of built-in functions. If you just want to see what's available and how to use them, it's best to refer to the reference.

RSL does not allow defining your own functions

RSL currently does not allow you to define your own functions, so any function you use is built-in.

Summary

  • Function invocation syntax is similar to most other C-like languages such as Python, Java, etc.
  • Functions may take no arguments, a fixed number of arguments, a varying number of args, and/or named arguments.
  • RSL does not allow you to define your own functions - all functions are built-in.

Next

We've already covered the Basics of strings, but there are some more advanced string concepts which are worth covering, such as string interpolation, raw strings, etc. We'll cover these in the next section: Strings (Advanced)!