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fn x [] = [] means that if the second argument to fn is an empty list, return an empty list. fn x (True:ys) = x : fn x ys means that if the second argument to fn starts with True, return a list th...
Answer
#1: Initial revision
by
r~~
·
2022-11-22T17:33:10Z (about 2 years ago)
`fn x [] = []` means that if the second argument to `fn` is an empty list, return an empty list. `fn x (True:ys) = x : fn x ys` means that if the second argument to `fn` starts with `True`, return a list that starts with the first argument to `fn` and continues with `fn x` applied to the remainder of the input list. `fn x _ = []` means that if the second argument to `fn` is anything not covered by the previous cases, return an empty list. (This line means that the first line in the definition of `fn` is actually unnecessary.) To synthesize, `fn x` takes a list and returns a list made of as many copies of `x` as there are consecutive `True` values at the start of the input list.