Clarified grammar BNF some

schala-lang/src/parsing.rs

@@ -14,51 +14,68 @@ use builtin::{BinOp, PrefixOp};
 /* Terminal productions are in 'single quotes' or UPPERCASE if they are a class
  * or not representable in ASCII
 
+
+/* Top-level Structure */
+
 program := (statement delimiter)* EOF
 delimiter := NEWLINE | ';'
 statement := expression | declaration
+block := '{' (statement delimiter)* '}'
 
 declaration := type_declaration | func_declaration | binding_declaration | impl_declaration
 
+/* Declarations - Types */
+
 type_declaration := 'type' type_declaration_body
 type_declaration_body := 'alias' type_alias | type_singleton_name '=' type_body
 type_alias := IDENTIFIER '=' type_name
 type_body := variant_specifier ('|' variant_specifier)*
-
 variant_specifier := IDENTIFIER | IDENTIFIER '{' typed_identifier_list '}' | IDENTIFIER '(' type_name* ')'
 typed_identifier_list := typed_identifier*
 typed_identifier := IDENTIFIER type_anno
 
+/* Declaration - Functions */
+
 func_declaration := func_signature func_body
 func_body := ε | '{' (statement delimiter)* '}'
 func_signature := 'fn' IDENTIFIER formal_param_list func_body
 formal_param_list := '(' (formal_param ',')* ')'
 formal_param := IDENTIFIER type_anno+
 
-binding_declaration: 'var' IDENTIFIER '=' expression
-                      | 'const' IDENTIFIER '=' expression
+/* Declaration - Variable bindings */
+
+binding_declaration: 'var' IDENTIFIER '=' expression | 'const' IDENTIFIER '=' expression
+
+/* Declaration - Interface */
 
 interface_declaration := 'interface' interface_name signature_block
 impl_declaration := 'impl' IDENTIFIER decl_block | 'impl' interface_name 'for' IDENTIFIER decl_block
-
 decl_block := '{' (func_declaration)* '}'
 signature_block := '{' (func_signature)* '}'
-
 interface_name := IDENTIFIER
 
+/* Type annotations */
+
 type_anno := (':' type_name)+
 type_name := type_singleton_name | '(' type_names ')'
 type_names := ε | type_name (, type_name)*
 type_singleton_name = IDENTIFIER (type_params)*
 type_params := '<' type_name (, type_name)* '>'
 
+
+/* Expressions */
+
 expression := precedence_expr type_anno+
 precedence_expr := prefix_expr
 prefix_expr := prefix_op call_expr
 prefix_op := '+' | '-' | '!' | '~'
 call_expr := index_expr ( '(' expr_list ')' )*
+expr_list := expression (',' expression)* | ε
 index_expr := primary ( '[' (expression (',' (expression)* | ε) ']' )*
 primary := literal | paren_expr | if_expr | match_expr | for_expr | while_expr | identifier_expr | curly_brace_expr | list_expr
+
+/* Primary Expressions */
+
 curly_brace_expr := lambda_expr | anonymous_struct //TODO
 list_expr := '[' (expression, ',')* ']'
 lambda_expr := '{' '|' (formal_param ',')* '|' (type_anno)* (statement delimiter)* '}'
@@ -66,42 +83,42 @@ paren_expr := LParen paren_inner RParen
 paren_inner := (expression ',')*
 identifier_expr := named_struct | IDENTIFIER
 
-literal := 'true' | 'false' | number_literal | STR_LITERAL
+/* Expression - Literals */
 
+literal := 'true' | 'false' | number_literal | STR_LITERAL
 named_struct := IDENTIFIER record_block
 record_block :=  '{' (record_entry, ',')* | '}' //TODO support anonymus structs, update syntax
 record_entry := IDENTIFIER ':' expression
 anonymous_struct := TODO
 
-if_expr := 'if' expression block else_clause
-else_clause := ε | 'else' block
-
-match_expr := 'match' expression match_body
-match_body := '{' (match_arm)* '}'
-match_arm := pattern '=>' expression
-pattern := identifier //TODO NOT DONE
-
-block := '{' (statement delimiter)* '}'
-
-expr_list := expression (',' expression)* | ε
-
-while_expr := 'while' while_cond '{' (statement delimiter)* '}'
-while_cond := ε | expression | expression 'is'  pattern //TODO maybe is-expresions should be primary
-
-//TODO this implies there must be at least one enumerator, which the parser doesn't support right
-//this second, and maybe should fail later anyway
-for_expr := 'for' (enumerator | '{' enumerators '}') for_expr_body
-for_expr_body := 'return' expression |  '{' (statement delimiter)* '}
-enumerators := enumerator (',' enumerators)*
-enumerator :=  identifier '<-' expression | identifier '=' expression //TODO add guards, etc.
-
-
 // a float_literal can still be assigned to an int in type-checking
 number_literal := int_literal | float_literal
 int_literal = ('0x' | '0b') digits
 float_literal := digits ('.' digits)
 digits := (DIGIT_GROUP underscore)+
 
+/* Expression - If */
+if_expr := 'if' expression block else_clause
+else_clause := ε | 'else' block
+
+/* Expression - Match */
+match_expr := 'match' expression match_body
+match_body := '{' (match_arm)* '}'
+match_arm := pattern '=>' expression
+pattern := identifier //TODO NOT DONE
+
+
+/* Expression - While */
+while_expr := 'while' while_cond '{' (statement delimiter)* '}'
+while_cond := ε | expression | expression 'is'  pattern //TODO maybe is-expresions should be primary
+
+//TODO this implies there must be at least one enumerator, which the parser doesn't support right
+//this second, and maybe should fail later anyway
+/* Expression - For */
+for_expr := 'for' (enumerator | '{' enumerators '}') for_expr_body
+for_expr_body := 'return' expression |  '{' (statement delimiter)* '}
+enumerators := enumerator (',' enumerators)*
+enumerator :=  identifier '<-' expression | identifier '=' expression //TODO add guards, etc.
 */
 
 type TokenIter = Peekable<IntoIter<Token>>;