The usefulness of the F. F: family (there will probably be just 1 or 2 
vocabulary entries) is that they replace / and /\ when the result of    u/ 
item_of_y (with optional initial value) is a different shape than item_of_y.  
Most often it is the shape of the initial value, though with F. that initial 
value can change to any shape as the items of y are applied to it.

Z: allows breaking out of such a fold when a condition is reached (usually a 
success condition for finding what you were looking for)

Z: might also be usable when wishing to exit/abort an arbitrary verb, for 
example, finding the first value that meets threshold

(1 i.~ 20 < ])@:+: i.10000000

could become, something like

>:@#  Z:^:(20 <])@:+:

though this needs work, and probably Z: needs to be an adverb that has its 
abort condition as u, which might lose flexibility for its main purpose with F.

From: Brian Schott <>
To: Programming forum <> 
Sent: Friday, March 2, 2018 1:02 PM
Subject: Re: [Jprogramming] Insert initialising

Have you considered using Z and z instead of Z and F?
And maybe using z and Z for the parallels to .: and :. although .: and :.
might be more suggestive of the distinctions that they make.
I frankly have a very hard time grokking all the different folds, not
having used any at all. But I am sort of not looking forward to the revised
Vocabulary page with the several F's added.

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