Luna is a data processing language and like every language it provides a syntax. However, in contrast to majority of languages Luna has more than one syntax representation – visual and textual. This chapter describes the later – the code. In order to use Luna efficiently you should learn both of them – the visual representation uses the textual one to define component's expressions.
Luna was designed to be a highly readable language. While designing its textual representation the main focus was creating a clean, concise and expressive syntax.
Luna code is indentation sensitive, which means that logically nested expressions are also visually nested in code. The layout was designed to maximally increase code readability and layout flexibility. There are three rules describing how it works:
- Each block can start in current or a new line. The block's indentation level is the same as it's first expression's indentation;
- Each nested code block should have bigger indentation level than the parent's one.
- Expressions can span over multiple lines, but all the spanned lines have to be indented more than the expression itself.
Luna does not allow mixing the use of tabs and spaces, only spaces are allowed for making code indentations. Almost every block starts with the colon
: operator. Here are some examples of different usages of indentation layout. You do not have to understand the code yet, it's important however to feel how the layout works.
# inline expression def sum a b: a + b # standard function declaration with indented code block def main: v = Vector 1 2 3 print $ checkVector v
The following example is invalid:
# ERROR: Indentation level does not match the first expression's one def main: v = Vector 1 2 3 print $ checkVector v
Scopes define when a particular name is accessible in a program. Each code block creates a distinct name scope, inheriting the names from the parent one. All the names of entities defined in a scope cannot escape its boundaries, in particular they cannot be accessed from the parent scope.