Logic

You write behaviour in three kinds of callable.

A variable never changes unless you write var mut, and every variable states its type (Values and types).

A constant names a fixed value at the top of a file.

A body is a list of statements, one on each line, with no semicolons.

"Widening" is one type standing in for another it is built on (When one type can stand in for another).

match chooses between the cases of a value.

A call that can fail must say so where it is called.

for item in items goes through a list, and the loop variable takes its type from the list.

You can pass an inline function only as an argument to a standard-library operation, such as list.map or list.filter.

A function may call itself, or form a cycle with other functions.

Only the standard library is generic (List<T>, list.count).