Formal grammar

This mirrors the recursive-descent structure of the parser directly.

program        → (NEWLINE | statement)* EOF

statement      → varDecl | assignment | showStmt | ifStmt
               | whileStmt | repeatStmt | functionDecl | returnStmt
               | exprStmt

varDecl        → "let" IDENTIFIER "be" expression NEWLINE
assignment     → "set" IDENTIFIER "to" expression NEWLINE
showStmt       → "show" expression NEWLINE
ifStmt         → "if" expression NEWLINE block ("otherwise" NEWLINE block)?
whileStmt      → "while" expression NEWLINE block
repeatStmt     → "repeat" expression "times" "as" IDENTIFIER NEWLINE block
functionDecl   → "define" IDENTIFIER "taking" params NEWLINE block
returnStmt     → "return" expression NEWLINE
exprStmt       → expression NEWLINE

block          → INDENT statement+ DEDENT

expression     → logicOr
logicOr        → logicAnd ( "or" logicAnd )*
logicAnd       → equality ( "and" equality )*
equality       → comparison ( ("==" | "!=") comparison )*
comparison     → term ( ("<" | "<=" | ">" | ">=") term )*
term           → factor ( ("+" | "-") factor )*
factor         → unary ( ("*" | "/" | "%") unary )*
unary          → ("not" | "-") unary | call
call           → primary ( "(" arguments? ")" )?
primary        → NUMBER | STRING | "true" | "false"
               | IDENTIFIER | "(" expression ")"