Even obvious dyadic functions like assertEquals(expected, actual) are problematic. How many times have you put the actual where the expected should be? The two arguments have no natural ordering. The expected, actual ordering is a convention that requires practice to learn. Dyads aren’t evil, and you will certainly have to write them. However, you should be aware that they come at a cost and should take advantage of what mechanims may be available to you to convert them into monads. For example, you might make the writeField method a member of outputStream so that you can say outputStream.
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