Haskell:TVar:orElse [英] Haskell: TVar: orElse

问题描述

是的其他"部分orElse 在由于另一个事务写入已读取的TVar而重试某个事务时调用，或者仅在

Is the "else" part of orElse called when a transaction is retried due to another transaction writing to a TVar it had read, or only when retry is explicitly called?

推荐答案

如果有

orElse a b

orElse a b

然后，只有在a中显式调用retry时，才会运行b.否则，orElse本质上将变得不确定. (由STM运行时完成的事务的重新运行是透明的，不应影响任何计算的结果.)

then b is only run if retry is called explicitly in a. Otherwise orElse would essentially become nondeterministic. (The rerunning of transactions that is done by the STM runtime is transparent and should not effect the outcome of any computation.)

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