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m (b i e) Converts an immutable array into a mutable array without taking a copy. This function is "unsafe" because any subsequent modifications made to the mutable version of

"unsafeThaw :: (Ix i, IArray a e, MArray b e m) => a i e - the array will be shared with the immutable version. It is safe to use, therefore, if the immutable version is never referenced again. "

The documentation is a bit misleading. It should say something like: Converts an immutable array into a mutable array. The implementation may either simply cast the array from one type to the other without copying the array, or it may take a full copy of the array. The non-copying implementation is supported between certain pairs of array types only; one constraint is that the array types must have identical representations. The following pairs of array types have a non-copying O(1) implementation of unsafeThaw: * UArray -> IOUArray * UArray -> STUArray * Array -> IOArray * Array -> STArray Note that because the array is possibly not copied, any subsequent modifications made to the mutable version of the array may be shared with the immutable version. It is safe to use, therefore, if the immutable version is never referenced again. Note in particular that unsafeThaw to a StorableArray currently doesn't have an efficient implementation. I'll update the docs with the text above. Cheers, Simon