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In the last video I used template 
blending to pretty quickly come up with 

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the solve function. 
What I didn't do in that video was to 

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write out the two wish list entries for 
the function we came up with. 

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And that's what I'm going to do now. 
We ended up right here, and the two 

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functions that we wished for but didn't 
define are solved and next boards. 

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So let's go ahead and do wish list 
entries for those. 

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Let's see. 
Solved, we give it a board, and we 

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want to know, is this board a final 
solution. 

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That's a yes. 
No question. 

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So it's going to produce a Boolean and 
it's produce true if board is solved. 

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Now what does solved mean? 
Well the way we generate the tree we only 

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put into the tree valid boards. 
So actually if we have a board that's 

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full. 
If we have a board that has no empty 

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space in it, then it's solved. 
So we could just note, assume board is 

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valid, so it is solved if it is full. 
This is a wish list entry, so we'll mark 

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that. 
And we'll do a stub. 

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So that's the wish list entry for solved. 
The other function that we named in 

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solved but we didn't do a wish list for, 
it doesn't exist yet, is next-boards. 

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See next-boards is right here. 
And what does next-boards do? 

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Well, next-boards consumes a board and it 
has to produce a list of board and, what 

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does it need to do? 
It needs to produce list of valid [SOUND] 

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next boards, from board. 
[BLANK_AUDIO] Here's a case, this 

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function's a little bit complicated now. 
Maybe we're going to want to expand on 

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our 78 character rule. 
Then you might want to say a bit more 

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about what it does. 
What it basically does is finds first 

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empty square, fills it with [1, 9] and it 
keeps only the valid boards. 

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And maybe I'll just make it more clear 
that's natural 1 to 9. 

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And this is also wish list entry. 
Bang, bang, bang. 

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And there's the stub. 
From here on out, this is a series of how 

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to design function problems. 
What I'm going to do is provide video 

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lectures for some of them. 
But they're really good practice, so you 

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might want to try some of them on your 
own. 

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I will say this. 
As you design these function you're 

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going to end up using a number of helper 
functions. 

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You'll end up using a number of the 
helper function rules that we've used. 

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So, there is a little bit of work, to do 
here. 

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All of it in some sense is review, 
although a couple of the functions are a 

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bit tricky. 
So what you might want to do is start 

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working on them. 
Look at the video solution. 

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Go back and forth. 
Anyways, I'll end this video here with 

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the wish list entries, and we'll pick up 
later with the solution to some of these. 

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[BLANK_AUDIO]