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metadesk/tests/grammar.md
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/* MetaDesk grammar with semantic annotations
*
* Each line represents a BNF-esque production:
* symbol : rule_1 | ... | rule_n
* - Pipe signs indicate mutually exclusive alternatives
* - Square quotes denote optional rules
* - Character literals are terminal productions
* - Tags indicate which way the productions attach to the generated tree (@child, @sibling, @tag)
* and miscellaneous semantics (@fill, @markup)
*/
//// A bunch of common definitions
separator : ' ' | unscoped_separator
unscoped_separator : '\n'| ',' | ';'
alt_scope_beg : '(' | '['
alt_scope_end : ')' | ']'
id : alpha [alphanumeric] | '_' [alphanumeric]
alphanumeric : alpha [alphanumeric] | digit [alphanumeric] | '_' [alphanumeric]
alpha : lowercase | uppercase
lowercase : 'a'|'b'|'c'|'d'|'e'|'f'|'g'|'h'|'i'|'j'|'k'|'l'|'m'|'n'|'o'|'p'|'q'|'r'|'s'|'t'|'u'|'v'|'w'|'z'|'y'|'z'
uppercase : 'A'|'B'|'C'|'D'|'E'|'F'|'G'|'H'|'I'|'J'|'K'|'L'|'M'|'N'|'O'|'P'|'Q'|'R'|'S'|'T'|'U'|'V'|'W'|'Z'|'Y'|'Z'
digit : '0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9'
label : id | integer_literal | char_literal | string_literal | symbol_label
integer_literal : { ['-'] natural_literal }
natural_literal : digit [natural_literal]
char_literal : @markup '\'' [char_literal_items] @markup '\''
char_literal_items : char_literal_item [char_literal_items]
char_literal_item : ascii_no_backslash_no_quotes | '"' | '\\' ascii
ascii : ascii_no_backslash_no_quotes | '\'' | '"' | '`' | '\\'
ascii_no_backslash_no_quotes : digit | alpha | symbol_no_backslash_no_quotes | ' '
symbol_no_backslash_no_quotes : symbol_no_backslash_no_quotes_1 | symbol_no_backslash_no_quotes_2
symbol_no_backslash_no_quotes_1 : '!'|'#'|'$'|'%'|'&'|'('|')'|'*'|'+'|','|'-'|'.'|'/'|':'
symbol_no_backslash_no_quotes_2 : ';'|'<'|'='|'>'|'?'|'@'|'['|']'|'^'|'_'|'{'|'|'|'}'|'~'
string_literal : @markup '"' [string_literal_items] @markup '"' | @markup '`' [string_literal_items] @markup '`'
string_literal_items : string_literal_item [string_literal_items]
string_literal_item : ascii_no_backslash_no_quotes | '\'' | '\\' ascii
symbol_label : '~'|'!'|'%'|'^'|'&'|'*'|'+'|'-'|'/'|'|'|'<'|'>'|'$'|'='|'.'|'?'|'$'
//// Arbitrarily deep tree, possibly empty
// file : [@child set_list]
// set_list : '{' [@child set_list] '}' [separator @sibling set_list]
//// Labeled leaves
// file : [@child set_list]
// set_list : set [separator @sibling set_list]
// set : @fill 'A' | '{' [@child set_list] '}'
//// Labeled internal nodes
// file : [@child set_list]
// set_list : set [separator @sibling set_list]
// set : @fill 'A' | [@fill 'A' ':'] '{' [@child set_list] '}'
//// Unscoped sets
// file : [@child set_list]
// set_list : scoped_set [separator @sibling set_list] | unscoped_set [unscoped_separator @sibling set_list]
// scoped_set : '{' [@child set_list] '}'
// unscoped_set : @fill 'A' [unscoped_set_tail]
// unscoped_set_tail : ':' @child unscoped_set | ' ' @sibling unscoped_set | ':' scoped_set |' ' @sibling scoped_set
//// Tags
// file : [@child set_list]
// set_list : scoped_set [separator @sibling set_list] | unscoped_set [unscoped_separator @sibling set_list]
// scoped_set : {[tag_list] '{' [@child set_list] '}'}
// unscoped_set : {[tag_list] @fill 'A' [unscoped_set_tail]}
// tag_list : '@' @tag tag ' ' [tag_list]
// tag : @fill 'T'['(' [@child set_list] ')']
// // unscoped_set_tail : ':' @child unscoped_set | ' ' @sibling unscoped_set | ':' @child scoped_set | ' ' @sibling scoped_set
// unscoped_set_tail : {':' @child unscoped_set | ' ' @sibling unscoped_set | set_tail_hack | ' ' @sibling scoped_set}
// // NOTE(mal): Ideally the set_tail_hack should be captured by the simpler
// // ':' @child scoped_set
// // but there's a quirk in the grammar.
// // In "A:{}", A has no children but in "A:@T{}", it has one tagged children,
// // which means that *the presence of tags* introduces the child
// set_tail_hack : ':' [@child tag_list] '{' '}' | ':' @child [tag_list] '{' @child set_list '}'
//// Alternative scope markers
// file : [@child set_list]
// set_list : scoped_set [separator @sibling set_list] | unscoped_set [unscoped_separator @sibling set_list]
// scoped_set : {[tag_list] untagged_scoped_set}
// untagged_scoped_set : '{' [@child set_list] '}' | alt_scope_beg [@child set_list] alt_scope_end
// unscoped_set : {[tag_list] @fill 'A' [unscoped_set_tail]}
// tag_list : '@' @tag tag ' ' [tag_list]
// tag : @fill 'T'['(' [@child set_list] ')']
// unscoped_set_tail : {':' @child unscoped_set | ' ' @sibling unscoped_set | set_tail_hack | ' ' @sibling scoped_set}
// set_tail_hack : {':' [@child tag_list] '{' '}' |
// ':' @child [tag_list] '{' @child set_list '}' |
// ':' [@child tag_list] alt_scope_beg alt_scope_end |
// ':' @child [tag_list] alt_scope_beg @child set_list alt_scope_end
// }
//// General tags and labels
file : [@child set_list]
set_list : scoped_set [separator @sibling set_list] | unscoped_set [unscoped_separator @sibling set_list]
scoped_set : {[tag_list] untagged_scoped_set}
untagged_scoped_set : '{' [@child set_list] '}' | alt_scope_beg [@child set_list] alt_scope_end
unscoped_set : {[tag_list] @fill label [unscoped_set_tail]}
tag_list : '@' @tag tag ' ' [tag_list]
tag : @fill id['(' [@child set_list] ')']
unscoped_set_tail : {':' @child unscoped_set | ' ' @sibling unscoped_set | set_tail_hack | ' ' @sibling scoped_set}
set_tail_hack : {':' [@child tag_list] '{' '}' |
':' @child [tag_list] '{' @child set_list '}' |
':' [@child tag_list] alt_scope_beg alt_scope_end |
':' @child [tag_list] alt_scope_beg @child set_list alt_scope_end
}
//// Comments before
//// TODO: This needs some work to make sure that "a /* comment_before_b */ b" can't be generated
//// but that "a /* comment_after_a */ b" can
// file : [@child set_list]
// set_list : scoped_set [separator @sibling set_list] | unscoped_set [unscoped_separator @sibling set_list]
// scoped_set : {[tag_list] [@pre_comment pre_comment] untagged_scoped_set}
// pre_comment : '/' '/' [' '] [@fill c_code_content] '\n' | '/' '*' [@fill cpp_code_content] '*' '/'
// c_code_content : 'c''o''m''m''e''n''t' // TODO: Arbitrary strings, including C-style comments, as long as /* */ pairs are balanced
// cpp_code_content : 'c''o''m''m''e''n''t' // TODO: Arbitrary strings that don't start with space
// untagged_scoped_set : '{' [@child set_list] '}' | alt_scope_beg [@child set_list] alt_scope_end
// unscoped_set : {[tag_list] @fill label [unscoped_set_tail]}
// tag_list : '@' @tag tag ' ' [tag_list]
// tag : @fill id['(' [@child set_list] ')']
// unscoped_set_tail : {':' @child unscoped_set | ' ' @sibling unscoped_set | set_tail_hack | ' ' @sibling scoped_set}
// set_tail_hack : {':' [@child tag_list] '{' '}' |
// ':' @child [tag_list] '{' @child set_list '}' |
// ':' [@child tag_list] alt_scope_beg alt_scope_end |
// ':' @child [tag_list] alt_scope_beg @child set_list alt_scope_end
// }