From b68ca45e7c443b4514dbb82634dcb5cc523a2b61 Mon Sep 17 00:00:00 2001
From: Jens Nolte <git@queezle.net>
Date: Mon, 4 Oct 2021 15:03:09 +0200
Subject: [PATCH] Add afix function (like mfix, but the value is passed as an
awaitable)
---
src/Quasar/Awaitable.hs | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/src/Quasar/Awaitable.hs b/src/Quasar/Awaitable.hs
index 4a07aed..47ff577 100644
--- a/src/Quasar/Awaitable.hs
+++ b/src/Quasar/Awaitable.hs
@@ -13,7 +13,8 @@ module Quasar.Awaitable (
awaitableFromSTM,
-- * Awaitable helpers
-
+ afix,
+ afix_,
awaitSuccessOrFailure,
-- ** Awaiting multiple awaitables
@@ -370,6 +371,22 @@ awaitSuccessOrFailure = await . fireAndForget . toAwaitable
fireAndForget :: MonadCatch m => m r -> m ()
fireAndForget x = void x `catchAll` const (pure ())
+afix :: (MonadIO m, MonadCatch m) => (Awaitable a -> m a) -> m a
+afix action = do
+ var <- newAsyncVar
+ catchAll
+ do
+ result <- action (toAwaitable var)
+ putAsyncVar_ var result
+ pure result
+ \ex -> do
+ failAsyncVar_ var ex
+ throwM ex
+
+afix_ :: (MonadIO m, MonadCatch m) => (Awaitable a -> m a) -> m ()
+afix_ = void . afix
+
+
-- ** Awaiting multiple awaitables
--
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