Parse Boolean literals.

joy/parser.py

@@ -41,6 +41,7 @@ from .utils.stack import list_to_stack
 
 
 #TODO: explain the details of float lits and strings.
+BOOL = 'true|false'
 FLOAT = r'-?\d+\.\d*(e(-|\+)\d+)?'
 INT = r'-?\d+'
 SYMBOL = r'[•\w!@$%^&*()_+<>?|\/;:`~,.=-]+'
@@ -114,6 +115,7 @@ def _parse(tokens):
 
 
 _scanner = Scanner([
+	(                BOOL, lambda _, token: token == 'true'),
 	(               FLOAT, lambda _, token: float(token)),
 	(                 INT, lambda _, token: int(token)),
 	(              SYMBOL, lambda _, token: Symbol(token)),