Source and blocks

Jazz processes declarations and evaluates expressions in source order. Earlier bindings are available to later expressions; ordinary forward references are not. The final top-level expression is the result of a standalone program.

Fragment:

answer :: Int.
answer = 40 + 2.
answer.

Blocks introduce a lexical scope. Their statements run in order, bindings are visible to later statements in the block, and the last expression becomes the block's value.

Fragment:

{
  left = 20.
  right = 22.
  left + right.
}

A later binding with the same name replaces it only for subsequent statements in that scope. Existing values and closures keep the environment they captured. Warnings can report same-scope rebinding, shadowing of an outer name, and an unused block binding.

A module owns an entire source unit and cannot be nested. Imports, data types, capabilities, and operators belong at source or module scope; expression blocks contain ordinary bindings, signatures, and expressions. See the expression grammar for the exact forms and lexical grammar for comments and terminators.