-- Program ::= Stmts

-- Stmts ::= Stmt
--         | Stmt ‘;’ Stmts

-- Stmt ::= ident ‘=’ Expr
--         | Expr

-- Expr ::= Term Expr'

-- Expr' ::= e
--         | LogicalExpr
--         | not Expr'

-- LogicalExpr ::= MathExpr
--               | RelOp Term LogicalExpr

-- MathExpr    ::= MathExpr'
--               | AddOp  Term Expr'

-- MathExpr'    ::= Term
--               | AddOp  Term Expr'

-- Term ::= numConst
--        | stringConst
--        | BoolVal
--        | ident IdentExpr
--        | 'not' Expr
--        | '(' Expr ')'
--        | '[' Exprz ']'
--        | ‘[’ Expr ForQual Qualz ‘]’

-- IdentExpr ::= e
--             | '(' Exprz ')'

-- BoolVal ::= 'None' | 'True ' | 'False'

-- Oper ::= AddOp
--        | MultOp
--        | RelOp

-- AddOp   ::= ‘+’ | ‘-’
-- MultOp  ::= ‘*’ | ‘//’ | ‘%’
-- RelOp   ::= ‘==’ | ‘!=’ | ‘<’ | ‘<=’ | ‘>’ | ‘>=’ | ‘in’ | ‘not’ ‘in’


-- ForQual ::= ‘for’ ident ‘in’ Expr

-- IfQual ::= ‘if’ Expr

-- Qualz ::= e
--         | ForQual Qualz
--         | IfQual Qualz

-- Exprz ::= e
--         | Exprs

-- Exprs ::= Expr
--         | Expr ‘,’ Exprs

-- ident ::= (see text)
-- numConst ::= (see text)
-- stringConst ::= (see text)