Glossary¶

Many concepts are universal across formats and languages, but are known by various names nonetheless. RCL adopts the following terminology.

Comprehension¶

A list, dict, or set comprehension is a way to construct a collection by iterating an existing collection. It is related to the idea of a for loop in imperative languages.

Dictionary¶

A dictionary, or dict for short, is a collection of key-value pairs where the keys are unique. A dict is called object in json, dict in Python, attrset in Nix, table in Lua, and associative array or map in many other languages.

In most places, using a dict in RCL looks the same as using a type with statically defined fields in other languages. In this sense, dicts also act as the analog of a struct or record in statically typed languages.

Function¶

Functions in RCL are anonymous: function values have no inherent name, but like any other value they can be bound to a name with a let binding. Functions are closures: they can capture values defined outside of the function body. Such functions are sometimes called lambda functions or lambdas in other languages.

If-else expression¶

Like everything in RCL, if-else is an expression, not control flow for statements. Some languages have a ternary operator that plays the same role. For example, cond ? x : y in C, or x if cond else y in Python, would be written if cond: x else: y in RCL.

List¶

A list is an ordered collection of values, not necessarily unique. A list is called array in json.

Set¶

A set is a collection of values where each value occurs at most once.