parser port

cases in exp	status
simple_exp	✅
prec_app: NOT exp	✅
exp actual_args	✅
ARRAY_CREATE simple_exp simple_exp	✅
prec_unary_minus: MINUS/MINUS_DOT exp	✅
AST_DOT: exp AST_DOT exp	✅
exp SLASH_DOT exp	✅
PLUS: exp PLUS/MINUS/PLUS_DOT/MINUS_DOT exp	✅
EQUAL (left): exp EQUAL/LESS_GREATER/LESS /GREATER/LESS_EQUAL/GREATER_EQUAL exp	✅
COMMA: elems	✅
LESS_MINUS: simple_exp DOT LPAREN exp RPAREN LESS_MINUS exp	✅
prec_if: IF exp THEN exp ELSE exp	✅
SEMICOLON: exp SEMICOLON exp	✅
prec_let: LET IDENT EQUAL exp IN exp	✅
LET REC fundef IN exp	✅
LET LPAREN pat RPAREN EQUAL exp IN exp	✅