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[Merged by Bors] - feat(data/set/finite): add a version of prod_preimage for inj_on
#3342
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This was referenced Jul 12, 2020
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…3342) * rename `finset.prod_preimage` to `finset.prod_preimage_of_bij`; * new `prod_preimage` assumes `∀ x ∈ s, x ∉ range f, g x = 1`; * rename `finset.image_preimage` to `finset.image_preimage_of_bij`; * new `finset.image_preimage` says `image f (preimage s hf) = s.filter (λ x, x ∈ set.range f)`; * change the order of implicit arguments in the definition of `set.inj_on`; * add `prod_filter_of_ne`; * use `coe` instead of `subtype.val` in `prod_attach`; * add `finset.image_subset_iff`, `finset.image_subset_iff_subset_preimage`, `finset.map_subset_iff_subset_preimage`.
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prod_preimage for inj_onprod_preimage for inj_on
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…eanprover-community#3342) * rename `finset.prod_preimage` to `finset.prod_preimage_of_bij`; * new `prod_preimage` assumes `∀ x ∈ s, x ∉ range f, g x = 1`; * rename `finset.image_preimage` to `finset.image_preimage_of_bij`; * new `finset.image_preimage` says `image f (preimage s hf) = s.filter (λ x, x ∈ set.range f)`; * change the order of implicit arguments in the definition of `set.inj_on`; * add `prod_filter_of_ne`; * use `coe` instead of `subtype.val` in `prod_attach`; * add `finset.image_subset_iff`, `finset.image_subset_iff_subset_preimage`, `finset.map_subset_iff_subset_preimage`.
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finset.prod_preimagetofinset.prod_preimage_of_bij;prod_preimageassumes∀ x ∈ s, x ∉ range f, g x = 1;finset.image_preimagetofinset.image_preimage_of_bij;finset.image_preimagesaysimage f (preimage s hf) = s.filter (λ x, x ∈ set.range f);set.inj_on;prod_filter_of_ne;coeinstead ofsubtype.valinprod_attach;finset.image_subset_iff,finset.image_subset_iff_subset_preimage,finset.map_subset_iff_subset_preimage.