argExpr :: Parser Expr
argExpr = try register
       <|> try regIndirect
       <|> try regIndex
       <|> try binOp
       <|> antiQuote
argExpr :: Parser Expr
argExpr = try register
       <|> try regIndirect
       <|> try regIndex
       <|> try binOp
       <|> antiQuote
argExpr = try register
       <|> try regIndirect
       <|> try regIndex
       <|> try binOp
       <|> antiQuote