From 8735af77df840190d9cf9eed2cbe3d949113b5e2 Mon Sep 17 00:00:00 2001
From: Simon Michael <simon@joyful.com>
Date: Tue, 9 May 2023 10:08:52 -1000
Subject: [PATCH] lib: add toggleopt, for flags that toggle when repeated

---
 hledger-lib/Hledger/Data/RawOptions.hs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hledger-lib/Hledger/Data/RawOptions.hs b/hledger-lib/Hledger/Data/RawOptions.hs
index a498c7813..c2ad93c28 100644
--- a/hledger-lib/Hledger/Data/RawOptions.hs
+++ b/hledger-lib/Hledger/Data/RawOptions.hs
@@ -14,6 +14,7 @@ module Hledger.Data.RawOptions (
   unsetboolopt,
   appendopts,
   boolopt,
+  toggleopt,
   choiceopt,
   collectopts,
   stringopt,
@@ -59,6 +60,11 @@ appendopts new = overRawOpts (++new)
 boolopt :: String -> RawOpts -> Bool
 boolopt name = isJust . lookup name . unRawOpts
 
+-- | Like boolopt, except if the flag is repeated on the command line it toggles the value.
+-- An even number of repetitions is equivalent to none.
+toggleopt :: String -> RawOpts -> Bool
+toggleopt name rawopts = odd $ length [ n | (n,_) <- unRawOpts rawopts, n==name]
+
 -- | From a list of RawOpts, get the last one (ie the right-most on the command line)
 -- for which the given predicate returns a Just value.
 -- Useful for exclusive choice flags like --daily|--weekly|--quarterly...