### Do Notation

Do notation makes working with actions and other "monad" types more convenient.
Do-notation contains semicolon-separated do-lines inside `do.N`

... `end`

, where `N`

is a namespace.
`.N`

may be omitted, in which case `Action.`

is the namespace.

`N`

must be a namespace with these names defined: `map`

, `pure`

, `ap`

, `liftA2`

, `**`

, `>>`

, `>>=`

.
All of these names will be aliased from `N`

into the current namespace.

Do-lines are expressions or of the form `<pattern> <- <expression>`

.
The last line must be an expression.

`do.N expr; exprs... end`

is the same as`expr >>.N do.N exprs... end`

`do.N pat <- expr; exprs... end`

is the same as`expr >>=.N fn pat => do.N exprs... end`

`do.N expr end`

is the same as`expr`

Appropriate namespaces for do notation:

`Maybe.`

`List.`

`Function.`

`Either.`

`Action.`

(the default if`.N`

is omitted)