Buzz Syntax BNF Specification
For an example-driven explanation of the Buzz syntax, see the syntax cheatsheet. In what follows, we report a formal 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_” | 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