diff --git a/grammar.txt b/grammar.txt
index 962dfe0..7d3afb7 100644
--- a/grammar.txt
+++ b/grammar.txt
@@ -1,12 +1,12 @@
 expression ->
 	| sequence
-//	| apply
+	| apply
 	| unary
 	| binary
 	| let
 	| compound
 	| control
-	| field
+	| selector
 	| index
 	| identifier
 	| primary
@@ -19,22 +19,25 @@ operator ->
 	| "+" | "-" | "*" | "/"
 	| "|>" | "<|" | ">>" | "<<"
 	| "++" ;
-pattern -> "_" | record_pattern | variant_pattern | identifier ;
+pattern -> "_" | record_pattern | variant_pattern ;
 record_pattern -> "{" ( identifier ( "=" pattern )? ( "," identifier ( "=" pattern )? )* ) ( "|" identifier ) "}"
 variant_pattern -> "`" identifier ( "(" ( "_" | compound_pattern | identifier ) ")" )? ;
-let -> "let" pattern "=" expression ( "and" pattern "=" expression )* "in" expression ;
+parameters -> "(" ( identifier ( "," identifier )* )?")"
+let -> "let" ( identifier parameters? | pattern ) "=" expression ( "and" ( identifier parameters? | pattern ) "=" expression )* "in" expression ;
 control ->
 	| if
 	| when
 if -> "if" expression "then" expression "else" expression ;
-when -> "when" expression "is" ( pattern "=>" expression )+ ;
+when -> "when" expression "is" ( ( identifier | pattern ) "=>" expression )+ ;
 compound -> variant | record | list ;
 variant -> "`" identifier ( "(" expression ")" )? ;
 base_record -> expression ( "with" identifier "=" expression ( "," "with" identifier "=" expression )* )?
 record ->
 	"{" ( identifier ("=" expression)? ( "," identifier ("=" expression)? )* )? ( "|" base_record )* "}" ;
 list -> "[" ( expression ( "," expression )* )? "]" ;
-field -> expression "." identifier ;
-index -> expression "[" expression "]" ;
 identifier -> IDENTIFIER | "@" STRING ;
-primary -> NUMBER | STRING | identifier | "(" expression ")" ;
+operand -> ( NUMBER | STRING | identifier | "(" expression ")" ) ;
+selector -> "." identifier ;
+index -> "[" expression "]" ;
+arguments -> "(" ( "_" | expression ( "," ( "_" | expression ) )* )? ")" ;
+primary -> operand ( selector | index | arguments ) ;