What part of Hindley-Milner do you not understand?

Question

I swear there used to be a T-shirt for sale featuring the immortal words:

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What part of

Answer 1

How do I understand the Hindley-Milner rules?

Hindley-Milner is a set of rules in the form of sequent calculus (not natural deduction) that demonstrates that we can deduce the (most general) type of a program from the construction of the program without explicit type declarations.

The symbols and notation

First, let's explain the symbols, and discuss operator precedence