(* new version *)

program = {expression | comment};
comment = ";", [ascii];
expression = rvalue | assign;
rvalue = arith | compare | call | coll;
compare = rvalue, compare_op, rvalue;
arith = term, [term_op, term];
builtin = "write"; (* TODO: add more *)
call = "do", "(", builtin, {["," rvalue]}, ")";
compare_op = "eq" | "neq" | "gt" | "gte" | "lt" | "lte";
term_op = "+" | "-";
term = factor, [factor_op, factor];
factor_op = "*" | "/";
factor = real | "(", rvalue, ")" | ident;
real = {"-"}, double;
double = [digit], {".", [digit]};
assign = ident, "=", expression;
ident = alpha, [alpha];

(* old version *)

identifier = alpha, [{alpha, digit, "_"}];
coll = "[", rvalue, [{",", rvalue}], "]";
seq = "|", rvalue, [{",", rvalue}], "|";
real = {"-"}, digit, [".", {digit}];
collection = coll | seq;
builtin = "map" | "fold" | "filter" | "zip" | "read" | "write" | "length";
fn = "func", "(", [ident, {",", ident}], ")", "{", {state}, "}";
rvalue = (identifier | real | '(', expr, ')') | collection | fn;
arith = rvalue, ("+" | "-" | "*" | "/"), rvalue;
logic = rvalue, ("or" | "and", "xor");
condition = rvalue, ("<" | ">" | "==" | "<=" | ">="), rvalue;
binop = arith | logic | condition;
unop = "not";
expr = assign | ([unop] rvalue, [ binop, expr ] ('\n' | ';')); 
if = "if", expr, {state}, ["elif", expr, {state}], ["else", {state}], "done";
while = "while", expr, {state}, "done";
state = expr | if | while;
call = "do", "(", builtin, {",", rvalue}, ")";
assign = identifier, "=", (call | rvalue | expr);
program = {state}

(* missing return *)
(* no support for ';' yet *)
(* no support for 'elif' yet *)