| Copyright | (c) Ross Paterson 2008 |
|---|---|
| License | BSD-style |
| Maintainer | ross@soi.city.ac.uk |
| Stability | experimental |
| Portability | portable |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Numeric.Search.Range
Description
Binary search of a bounded interval of an integral type for the boundary of an upward-closed set, using a combination of exponential and binary search.
Synopsis
- searchFromTo :: Integral a => (a -> Bool) -> a -> a -> Maybe a
Documentation
searchFromTo :: Integral a => (a -> Bool) -> a -> a -> Maybe a Source #
O(log(h-l)). Search a bounded interval of some integral type.
If p is an upward-closed predicate, searchFromTo p l h == Just n if and only if n is the least number l <= n <= h satisfying p.
For example, the following function determines the first index (if any) at which a value occurs in an ordered array:
searchArray :: Ord a => a -> Array Int a -> Maybe Int searchArray x array = do let (lo, hi) = bounds array k <- searchFromTo (\ i -> array!i >= x) lo hi guard (array!k == x) return k