Osprey Flavors: Two Syntaxes, One Language

Osprey Flavors: Two Syntaxes, One Language

By Christian Findlay 3 min read

Osprey has two source flavors:

  • Default (.osp) uses braces, fn, named arguments and familiar calls.
  • ML (.ospml) uses layout, curry-by-default functions and whitespace application.

Each flavor has its own parser and lowerer. Both produce osprey_ast::Program before type checking, effect checking and code generation.

fn add(x) = fn(y) => x + y
add x y = x + y

The compiler tests these explicit-curry forms for AST equivalence. A Default multi-parameter function, such as fn add(x, y), is intentionally different: it accepts two arguments at once rather than returning a function.

ML layout and matching are available in runnable examples:

classify n =
    match n
        0 => "zero"
        1 => "one"
        _ => "many"

Flavor selection works per file through .osp or .ospml, a leading source marker, or --flavor for a single-file build. A project can mix both flavors and import across them.

Both flavors support effect, perform, handle and handler; see Effect Handlers You Can Call.

See the tested examples and language-flavor specification.