Internal documentation — Work in progress

This page has not been confirmed as accurate or approved for publication. Current documentation version: 0.1.0-internal.1.

Exceptions

Settled design vocabulary: hope starts protected code, unless introduces a handler, finally introduces cleanup, and scream raises an exception. Exceptions are intended to be the primary error mechanism.

Implemented in the parser: the four words are dedicated tokens and produce exception AST nodes. The grammar is:

hope_statement := "hope" block ("unless" expression block)* ("finally" block)?
scream_statement := "scream" expression

A hope must contain at least one unless or finally clause. Multiple handlers are accepted. finally, when present, is unique and last. Clauses follow the preceding closing brace without an intervening logical newline. Standalone unless and finally, a clause-free hope, and a value-free scream are syntax errors.

Open questions: exception types and handler matching, binding the caught value, propagation, stack unwinding, cleanup ordering, interaction with return and reference counting, and treatment of runtime errors such as overflow.

There is no semantic or runtime exception implementation yet.