From 90a96dee4947b5d67fdd6ca1e32e71a4985fe169 Mon Sep 17 00:00:00 2001
From: slotThe <soliditsallgood@mailbox.org>
Date: Wed, 17 Nov 2021 19:58:32 +0100
Subject: [PATCH] X.H.ManageHelpers: Flip logic for (^?), (~?), and ($?)

This changes how the "is*Of" infix operators are hoisted into the
ManageHook context.  Instead of `q ~? x` being a lifted version of
`isPrefixOf q x` we instead let it be a lift of `isPrefixOf x q`.

While this obviously does not matter for symmetric operators like `(==)`
and `(/=)`, for `isInfixOf` it is rather essential.  The reason for that
is that the given `q` on the left side is an atom that can't (shouldn't)
be changed (by the user) and we only have control over the right hand
side.  Otherwise, things like

    title ~? "foo"

would read "only match if `title` is an infix of `foo`" instead of the
much more useful "only match if `foo` is an infix of `title`".

Fixes: 8b6f17ba6684a126fc1bde8d7275c166b3456d37
---
 CHANGES.md                    |  7 ++++++-
 XMonad/Hooks/ManageHelpers.hs | 16 ++++++++--------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index 34065612..9a5cadb0 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -25,7 +25,12 @@
 
   * `XMonad.Util.EZConfig`
 
-    - Added support for Modifier Keys `KeySym`s for Emacs-like `additionalKeysP`
+    - Added support for Modifier Keys `KeySym`s for Emacs-like `additionalKeysP`.
+
+  * `XMonad.Hooks.ManageHelpers`
+
+    - Flipped how `(^?)`, `(~?)`, and `($?)` work to more accurately
+      reflect how one uses these operators.
 
 ## 0.17.0 (October 27, 2021)
 
diff --git a/XMonad/Hooks/ManageHelpers.hs b/XMonad/Hooks/ManageHelpers.hs
index b2ae327a..3f9dbac3 100644
--- a/XMonad/Hooks/ManageHelpers.hs
+++ b/XMonad/Hooks/ManageHelpers.hs
@@ -32,9 +32,9 @@
 -- > f :: a -> b -> Bool
 -- >
 -- > -- a new helper
--- > q ***? x = fmap (\a -> f a x) q
+-- > q ***? x = fmap (\a -> f a x) q   -- or: (\b -> f x b)
 -- > -- or
--- > q ***? x = fmap (`f` x) q
+-- > q ***? x = fmap (`f` x) q         -- or: (x `f`)
 --
 -- Any existing operator can be "lifted" in the same way:
 --
@@ -109,17 +109,17 @@ infixr 0 -?>, -->>, -?>>
 (/=?) :: (Eq a, Functor m) => m a -> a -> m Bool
 q /=? x = fmap (/= x) q
 
--- | q ^? x. if the result of q 'isPrefixOf' x, return True
+-- | q ^? x. if the result of @x `isPrefixOf` q@, return True
 (^?) :: (Eq a, Functor m) => m [a] -> [a] -> m Bool
-q ^? x = fmap (`isPrefixOf` x) q
+q ^? x = fmap (x `isPrefixOf`) q
 
--- | q ~? x. if the result of q 'isSuffixOf' x, return True
+-- | q ~? x. if the result of @x `isInfixOf` q@, return True
 (~?) :: (Eq a, Functor m) => m [a] -> [a] -> m Bool
-q ~? x = fmap (`isInfixOf` x) q
+q ~? x = fmap (x `isInfixOf`) q
 
--- | q $? x. if the result of q 'isSuffixOf' x, return True
+-- | q $? x. if the result of @x `isSuffixOf` q@, return True
 ($?) :: (Eq a, Functor m) => m [a] -> [a] -> m Bool
-q $? x = fmap (`isSuffixOf` x) q
+q $? x = fmap (x `isSuffixOf`) q
 
 -- | q <==? x. if the result of q equals x, return True grouped with q
 (<==?) :: (Eq a, Functor m) => m a -> a -> m (Match a)