v3 Parsing: Postfix Calls, Indexing, and Literals

Why this module exists

The parser must now handle richer expressions and nested function declarations. The grammar stays small but now includes postfix operators and literal collections.

1) Program grammar (v3)

program    -> stmt* EOF

stmt       -> varDecl
           | funDecl
           | ifStmt
           | whileStmt
           | returnStmt
           | block
           | assignStmt
           | exprStmt

funDecl    -> "fn" IDENT "(" params? ")" block
params     -> IDENT ("," IDENT)*

varDecl    -> ("let" | "var" | "const") IDENT ("=" expr)? ";"
assignStmt -> lvalue "=" expr ";"
exprStmt   -> expr ";"
block      -> "{" stmt* "}"

ifStmt     -> "if" "(" expr ")" block ("else" block)?
whileStmt  -> "while" "(" expr ")" block
returnStmt -> "return" expr? ";"

lvalue is an identifier with optional indexing:

lvalue -> IDENT ("[" expr "]")*

2) Expression grammar

expr       -> equality

equality   -> comparison ( ("==" | "!=") comparison )*
comparison -> term ( ("<" | "<=" | ">" | ">=") term )*
term       -> factor ( ("+" | "-") factor )*
factor     -> unary ( ("*" | "/") unary )*

unary      -> ("!" | "-") unary | postfix
postfix    -> primary ( call | index )*
call       -> "(" args? ")"
index      -> "[" expr "]"
args       -> expr ( "," expr )*

primary    -> NUMBER | STRING | TRUE | FALSE | NIL
          | IDENT
          | "(" expr ")"
          | arrayLit
          | mapLit

arrayLit   -> "[" (expr ("," expr)*)? "]"
mapLit     -> "{" (pair ("," pair)*)? "}"
pair       -> expr ":" expr

3) Block vs map literal

A { at statement level starts a block. A { inside an expression starts a map literal. That context split keeps parsing deterministic.

4) Readability

Postfix parsing is just a loop. Keep it simple.