BL creates Bool.

CL creates Char.

DL creates Double.

ID creates Ident.

IL creates Integer.

KW creates Keyword.

L creates List from a Expr vararg.

LL creates List from a slice of Exprs.

OP creates Operator.

SL creates String.

TP creates Type.

Keywords are language keywords.

Operators are language operators.

Bool is a boolean literal.

Char is a rune literal.

Double is a float64 literal.

Ident is an identifier.

Integer is an int literal.

Keyword is a language keyword.

List is a list.

Operator is an operator.

String is a string literal.

Type is an identifier.

Atom is an atom.

Expr is a generic s-expression.