Int -> [a] -> a -base
O(log n). replicate n x is a sequence consisting of n copies of x.
Indicates that it may be beneficial to evaluate the first argument in parallel with the second. Returns the value of the second argument.
a `par` b is exactly equivalent semantically to b.
par is generally used when the value of a is likely to be required later, but not immediately. Also it is a good idea to ensure that a is not a trivial computation, otherwise the cost of spawning it in parallel overshadows the benefits obtained by running it in parallel.
Note that actual parallelism is only supported by certain implementations (GHC with the -threaded option, and GPH, for now). On other implementations, par a b = b.
Semantically identical to seq, but with a subtle operational difference: seq is strict in both its arguments, so the compiler may, for example, rearrange a `seq` b into b `seq` a `seq` b. This is normally no problem when using seq to express strictness, but it can be a problem when annotating code for parallelism, because we need more control over the order of evaluation; we may want to evaluate a before b, because we know that b has already been sparked in parallel with par.
This is why we have pseq. In contrast to seq, pseq is only strict in its first argument (as far as the compiler is concerned), which restricts the transformations that the compiler can do, and ensures that the user can retain control of the evaluation order.
O(min(n,W)). The expression (findWithDefault def k map) returns the value at key k or returns def when the key is not an element of the map.
> findWithDefault 'x' 1 (fromList [(5,'a'), (3,'b')]) == 'x'
> findWithDefault 'x' 5 (fromList [(5,'a'), (3,'b')]) == 'a'
O(1). A map of one element.
> singleton 1 'a' == fromList [(1, 'a')]
> size (singleton 1 'a') == 1
O(1) drop n xs returns the suffix of xs after the first n elements, or  if n > length xs.
O(1) take n, applied to a ByteString xs, returns the prefix of xs of length n, or xs itself if n > length xs.
A variety of drop which omits the checks on n so there is an obligation on the programmer to provide a proof that 0 <= n <= length xs.
A variety of take which omits the checks on n so there is an obligation on the programmer to provide a proof that 0 <= n <= length xs.
O(n) drop n, applied to a Text, returns the suffix of the Text after the first n characters, or the empty Text if n is greater than the length of the Text. Subject to fusion.
O(1) Unchecked drop of k Word16s from the front of a Text.
O(n*m) replicate n t is a Text consisting of the input t repeated n times.
O(n) take n, applied to a Text, returns the prefix of the Text of length n, or the Text itself if n is greater than the length of the Text. Subject to fusion.
O(1) Unchecked take of k Word16s from the front of a Text.
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