1 files changed, 3 insertions, 2 deletions

diff --git a/grammar.bnf b/grammar.bnf
index 9ddaffc..0ac58f9 100644
--- a/grammar.bnf
+++ b/grammar.bnf
@@ -2,9 +2,10 @@
 
 program ::= (statement ';'?)*;
 statement ::= definition | expression;
-definition ::= 'def' def-spec '=' expression;
+definition ::= 'def' def-spec '=' expression
+             | 'def' '_' '=' expression;
 def-spec ::= IDENTIFIER arg-spec*;
-arg-spec ::= IDENTIFIER | '(' ')';
+arg-spec ::= IDENTIFIER | '(' ')' | '_';
 expression ::= binary-expression | unary-expression;
 unary-expression ::= unop+ simple-expression;
 binary-expression ::= call-expression (binop call-expression)*;