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Buzz Syntax BNF Specification

For an example-driven explanation of the Buzz syntax, see the Buzz API. 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_', "_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