| Both sides previous revision Previous revision | |
| buzz_syntax_bnf [2018/07/17 18:02] – ilpincy | buzz_syntax_bnf [2018/07/17 18:59] (current) – ilpincy |
|---|
| | ====== Buzz Syntax BNF Specification ====== |
| |
| | For an example-driven explanation of the Buzz syntax, see the [[buzz_syntax_cheatsheet|syntax cheatsheet]]. In what follows, we report a formal [[https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_Form|Backus-Naur Form grammar]] specification. |
| | ===== Tokens ===== |
| | |
| | An **identifier** in Buzz is defined by this regular expression: |
| | |
| | [[:alpha:]_][[:alnum:]_]* |
| | |
| | The recognized tokens are: |
| | |
| | ^ Token ^ Id ^ |
| | | //identifier// | ''TOKID'' | |
| | | //numeric constant// | ''TOKCONST'' | |
| | | '''''_string_''''' ''"''_string_''"'' | ''TOKSTRING'' | |
| | | ''var'' | ''TOKVAR'' | |
| | | ''nil'' | ''TOKNIL'' | |
| | | ''if'' | ''TOKIF'' | |
| | | ''else'' | ''TOKELSE'' | |
| | | ''function'' | ''TOKFUN'' | |
| | | ''return'' | ''TOKRETURN'' | |
| | | ''for'' | ''TOKFOR'' | |
| | | ''while'' | ''TOKWHILE'' | |
| | | ''and'', ''or'' | ''TOKLANDOR'' | |
| | | ''not'' | ''TOKLNOT'' | |
| | | ''+'', ''-'' | ''TOKADDSUB'' | |
| | | ''*'', ''/'' | ''TOKMULDIV'' | |
| | | ''%'' | ''TOKMOD'' | |
| | | ''^'' | ''TOKPOW'' | |
| | | ''<<'' ''>>'' | ''TOKLRSHIFT'' | |
| | | ''&'' ''|'' | ''TOKBANDOR'' | |
| | | ''!'' | ''TOKBNOT'' | |
| | | ''{'' | ''TOKBLOCKOPEN'' | |
| | | ''}'' | ''TOKBLOCKCLOSE'' | |
| | | ''('' | ''TOKPAROPEN'' | |
| | | '')'' | ''TOKPARCLOSE'' | |
| | | ''['' | ''TOKIDXOPEN'' | |
| | | '']'' | ''TOKIDXCLOSE'' | |
| | | '';'' ''\n'' | ''TOKSTATEND'' | |
| | | '','' | ''TOKLISTSEP'' | |
| | | ''='' | ''TOKASSIGN'' | |
| | | ''.'' | ''TOKDOT'' | |
| | | ''<'' ''<='' ''>'' ''>='' ''=='' ''!='' | ''TOKCMP'' | |
| | |
| | ===== Grammar ===== |
| | |
| | script ::= statlist |
| | |
| | statlist ::= stat | statlist stat |
| | stat ::= <nil> | vardef | fundef | if | loop | command |
| | |
| | block ::= TOKBLOCKOPEN statlist TOKBLOCKCLOSE |
| | |
| | vardef ::= TOKVAR TOKID | TOKVAR TOKID assignment |
| | fundef ::= TOKFUN TOKID TOKPAROPEN idlist TOKPARCLOSE block |
| | if ::= TOKIF TOKPAROPEN condition TOKPARCLOSE block endif |
| | endif ::= <nil> | TOKELSE block |
| | loop ::= forloop | whileloop |
| | forloop ::= TOKFOR TOKPAROPEN idref TOKASSIGN expression TOKLISTSEP condition TOKLISTSEP idref TOKASSIGN expression TOKPARCLOSE block |
| | whileloop ::= TOKWHILE TOKPAROPEN condition TOKPARCLOSE block |
| | |
| | conditionlist ::= condition | conditionlist TOKLISTSEP condition |
| | condition ::= comparison | condition TOKLANDOR comparison | TOKLNOT condition |
| | comparison ::= expression | expression TOKCMP expression |
| | |
| | expression ::= product | expression TOKADDSUB product |
| | product ::= modulo | product TOKMULDIV modulo |
| | modulo ::= power | modulo TOKMOD power |
| | power ::= bitshift powerrest |
| | powerrest ::= <nil> | TOKPOW power |
| | bitshift ::= bitwiseandor | operand TOKLRSHIFT bitwiseandor |
| | bitwiseandor ::= bitwisenot | bitwiseandor TOKBANDOR bitwisenot |
| | bitwisenot ::= operand | TOKBNOT bitwisenot |
| | operand ::= TOKNIL | TOKCONST | TOKSTRING | TOKPAROPEN condition TOKPARCLOSE | TOKADDSUB power | idref | lambda | tabledef |
| | |
| | command ::= idref | idref assignment | TOKRETURN expression |
| | assignment ::= TOKASSIGN expression |
| | |
| | tabledef ::= TOKBLOCKOPEN TOKBLOCKCLOSE | TOKBLOCKOPEN tablefielddeflist TOKBLOCKCLOSE |
| | tablefielddef ::= TOKDOT TOKID assignment | TOKDOT TOKCONST assignment |
| | tablefielddeflist ::= tablefielddef | tablefielddeflist TOKLISTSEP tablefielddef |
| | |
| | idlist ::= <nil> | TOKID | idlist TOKLISTSEP TOKID |
| | idreflist ::= idref | idreflist TOKLISTSEP idref |
| | idref ::= TOKID | idref TOKDOT TOKID | idref TOKIDXOPEN expression TOKIDXCLOSE | idref TOKPAROPEN conditionlist TOKPARCLOSE |
| | |
| | lambda ::= TOKFUN TOKPAROPEN idlist TOKPARCLOSE block |