问题
I am preparing for test in haskell and I found a task from last test where was given to generate infinite list lists.
generate :: Num n => n -> [[n]]
where list is n-tuple, n is from parameter.
moreover the lists has to be sorted.
For exaple:
generate 2 = [[0,0],[0,1],[1,0],[1,1],[0,2],[1,2],[2,0],[2,1],[2,2],[0,3],....]
I have to use only basic functions.
I know that it surely is simple, but I dont know how to do it and I also can't find it on the internet.
I will be really glad for any help.
回答1:
Here's a hint for the allTuplesWithMaxElem function...
Suppose you want to generate all lists [a,b,c,d] from the numbers [0..2] with the restriction that 2 must appear as one of the elements.
Consider these questions:
If we set a = 0, what are the possibilities for [b,c,d] ?
If we set a = 1, what are the possibilities for [b,c,d] ?
If we set a = 2, what are the possibilities for [b,c,d] ?
来源：https://stackoverflow.com/questions/37949703/haskell-generate-list-of-lists