Other Quiz: Elegant evaluations...

Erel · Oct 13, 2014

We need to implement a sub that calls several other subs in a specific order. Each of these subs returns True if the sub was executed successfully and false otherwise.

If any sub returned false then we should stop calling other subs and return false. If all subs returned true then we need to return true.

B4X:

Sub DoSeveralTasks As Boolean
'call TaskA. If good continue to TaskB and so on...
End Sub

Sub TaskA(...) As Boolean

End Sub

Sub TaskB(...) As Boolean

End Sub
'more subs here. Each with a different name and a different number of parameters.

Please use the Spoiler tag in your answer:

It is of course very simple to implement this. The challenge is to write an elegant solution.

LucaMs · Oct 13, 2014

James Chamblin said:
Yes, in my example I know.but what if I'm writing a class module or library where the Subs could be different depending on use? Then I wouldn't know ahead of time and a solution like#2 and #7 could come in handy.

In the moment in which you instantiate that class you know the names of your routines

James Chamblin · Oct 13, 2014

LucaMs said:
In the moment in which you instantiate that class you know the names of your routines

That is true; however the class does not know. How can I write a class that calls routines that I don't know when the class is written?

LucaMs · Oct 13, 2014

James Chamblin said:
That is true; however the class does not know. How can I write a class that calls routines that I don't know when the class is written?

You don't need that kind of "service" into (from) your class, just use #3

Troberg · Oct 13, 2014

James Chamblin said:
Yes, in my example I know.but what if I'm writing a class module or library where the Subs could be different depending on use? Then I wouldn't know ahead of time and a solution like#2 and #7 could come in handy.

Yep, say that you are evaluating a file where each line can hold a different type of object. Depending on what you find on a line, you call a different sub. On the other hand, I would probably use a Select, just to be sure. I mean, the subs needs to be known at compile time anyway, even if you don't know which you are going to call.

LucaMs · Oct 13, 2014

LucaMs said:
Can you lock the spoiler up to a deadline?

Forget it: I can read the html source

Well, until there are no prizes, we can trust the honesty of all the members of the site

Erel · Oct 13, 2014

LucaMs said:
Can you lock the spoiler up to a deadline?

No.

Derek Johnson · Jun 13, 2015

Sorry for late contribution. I am on intergalactic spaceship 0.4 parsec from Earth; only just saw quiz.

Updated answer - should have read the question first. (Very dim lighting in my spaceship).

B4X:

sub GetResults

select case FALSE
case sub1(a,bc)
case sub2(x,y)
case sub3(p,q,r)
case ...
case else 'All cases must have been true
   return TRUE
end select
'Must have encountered a false case
return FALSE
end sub

I think that's pretty readable. I always use this sort of construct rather than a whole bunch of if...then..else.

Derek

Derek Johnson · Jun 13, 2015

Derek Johnson said:
Sorry for late contribution. I am on intergalactic spaceship 0.4 parsec from Earth; only just saw quiz.

B4X:

sub GetResults select case true case sub1(a,bc) case sub2(x,y) case sub3(p,q,r) case ... case else return false end select return true end sub

I think that's pretty readable. I always use this sort of construct rather than a whole bunch of if...then..else.

Derek

Sorry - readable but wrong. Needed to invert all Trues and Falses then it works correctly.

Otherwise this stops after the first sub returns True., should continue to first false one. I misread the question. It's a useful construct sometimes though.

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