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Summary

Let `pt_1, .., pt_n` and `qt` be length-m tuples of patterns for the same type `(T_1, .., T_m)`. We compute `usefulness(tp_1, .., tp_n, tq)` as follows: 

I'm studying how the compiler implements pattern-matchings, and I'm confused with this sentence. It first introduces pt_1, .., pt_n, and uses names tp_1, .., tp_n.

Is this just a typo? or does the document introduce tp_1, .., tp_n but I'm unable to find one?

Thanks!

EDIT: rendered version