From d27936801b2997af16814e2879c8bdf6f4eb7bcc Mon Sep 17 00:00:00 2001
From: Cyril Cohen
Date: Mon, 18 Nov 2019 18:22:20 +0100
Subject: Adding `inj_compr` lemma in ssrfun.

---
 plugins/ssr/ssrfun.v | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'plugins')

diff --git a/plugins/ssr/ssrfun.v b/plugins/ssr/ssrfun.v
index b8affba541..dd847169b9 100644
--- a/plugins/ssr/ssrfun.v
+++ b/plugins/ssr/ssrfun.v
@@ -675,6 +675,9 @@ Proof. by move=> fK injf' x; apply: injf'. Qed.
 Lemma inj_comp : injective f -> injective h -> injective (f \o h).
 Proof. by move=> injf injh x y /injf; apply: injh. Qed.
 
+Lemma inj_compr : injective (f \o h) -> injective h.
+Proof. by move=> injfh x y /(congr1 f) /injfh. Qed.
+
 Lemma can_comp f' h' : cancel f f' -> cancel h h' -> cancel (f \o h) (h' \o f').
 Proof. by move=> fK hK x; rewrite /= fK hK. Qed.
 
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