Notation for Finsupp #
This file provides fun₀ | 3 => a | 7 => b notation for Finsupp, which desugars to
Finsupp.update and Finsupp.single, in the same way that {a, b} desugars to insert and
singleton.
fun₀ | i => a is notation for Finsupp.single i a, and with multiple match arms,
fun₀ ... | i => a is notation for Finsupp.update (fun₀ ...) i a.
As a result, if multiple match arms coincide, the last one takes precedence.
If the expected type is Π₀ i, α i (DFinsupp)
and Mathlib/Data/DFinsupp/Notation.lean is imported,
then this is notation for DFinsupp.single and Dfinsupp.update instead.