如何根据f中许多昂贵的计算结果来计算结果#

假设我有以下伪C代码:

TResult MyMethod()
{
    var firstTry = SomeExpensiveComputation1();
    if (firstTry.IsSuccessful) return firstTry;

    var secondTry = SomeExpensiveComputation2();
    if (secondTry.IsPartiallySuccessful)
    {
        var subTry1 = SomeExpensiveComputationOn2_1(secondTry);
        if (subTry1.IsSuccessful) return subTry1;

        var subTry1 = SomeExpensiveComputationOn2_2(secondTry);
        if (subTry1.IsSuccessful) return subTry1;
    }

    return LastExpensiveComputationThatNeverFails();
}

如果我是在f_做这个的话,它会是这样的:

let MyMethod () =
    let firstTry = SomeExpensiveComputation1 ()
    if firstTry.IsSuccessful then firstTry else
        let secondTry = SomeExpensiveComputation2 ()
        if secondTry.IsSuccessful then
            let subTry1 = SomeExpensiveComputationOn2_1 ()
            if subTry1.IsSuccessful then subTry1 else
                let subTry2 = SomeExpensiveComputationOn2_2 ()
                if subTry2.IsSuccessful then subTry2 else LastExpensiveComputationThatNeverFails ()
        else
            LastExpensiveComputationThatNeverFails()

正如你在上面看到的,我不得不重复 LastExpensiveComputationThatNeverFails 两次。这不必是一个方法调用,它可以是许多行内联计算(例如,尝试从缓存中获取一些值,如果它不存在,计算它)。可以将代码重构成另一个函数,但我仍然不喜欢相同的代码,即使它只是一行,必须写两次(或更多),因为这会导致重复和混乱的维护。用f_编写这种代码的正确方法是什么?