Some functions are flagged as not tail-recursive. A tail-recursive function uses constant stack space, while a non-tail-recursive function uses stack space proportional to the length of its list argument, which can be a problem with very long lists. When the function takes several list arguments, an approximate formula giving stack usage (in some unspecified constant unit) is shown in parentheses.
The above considerations can usually be ignored if your lists are not longer than about 10000 elements.
The labeled version of this module can be used as described in the StdLabels module.
Return the length (number of elements) of the given list.
Sourceval compare_lengths : 'a list->'b list-> int
Compare the lengths of two lists. compare_lengths l1 l2 is equivalent to compare (length l1) (length l2), except that the computation stops after reaching the end of the shortest list.
since 4.05
Sourceval compare_length_with : 'a list->int -> int
Compare the length of a list to an integer. compare_length_with l len is equivalent to compare (length l) len, except that the computation stops after at most len iterations on the list.
Concatenate a list of lists. The elements of the argument are all concatenated together (in the same order) to give the result. Not tail-recursive (length of the argument + length of the longest sub-list).
equal eq [a1; ...; an] [b1; ..; bm] holds when the two input lists have the same length, and for each pair of elements ai, bi at the same position we have eq ai bi.
Note: the eq function may be called even if the lists have different length. If you know your equality function is costly, you may want to check compare_lengths first.
since 4.12
Sourceval compare : ('a->'a-> int)->'a list->'a list-> int
compare cmp [a1; ...; an] [b1; ...; bm] performs a lexicographic comparison of the two input lists, using the same 'a -> 'a -> int interface as Stdlib.compare:
a1 :: l1 is smaller than a2 :: l2 (negative result) if a1 is smaller than a2, or if they are equal (0 result) and l1 is smaller than l2
the empty list [] is strictly smaller than non-empty lists
Note: the cmp function will be called even if the lists have different lengths.
for_all f [a1; ...; an] checks if all elements of the list satisfy the predicate f. That is, it returns (f a1) && (f a2) && ... && (f an) for a non-empty list and true if the list is empty.
exists f [a1; ...; an] checks if at least one element of the list satisfies the predicate f. That is, it returns (f a1) || (f a2) || ... || (f an) for a non-empty list and false if the list is empty.
Same as find_map, but the predicate is applied to the index of the element as first argument (counting from 0), and the element itself as second argument.
Sourceval filteri : (int ->'a-> bool)->'a list->'a list
Same as filter, but the predicate is applied to the index of the element as first argument (counting from 0), and the element itself as second argument.
Sourceval take_while : ('a-> bool)->'a list->'a list
take_while p l is the longest (possibly empty) prefix of l containing only elements that satisfy p.
since 5.3
Sourceval drop_while : ('a-> bool)->'a list->'a list
drop_while p l is the longest (possibly empty) suffix of l starting at the first element that does not satisfy p.
since 5.3
Sourceval partition : ('a-> bool)->'a list->'a list * 'a list
partition f l returns a pair of lists (l1, l2), where l1 is the list of all the elements of l that satisfy the predicate f, and l2 is the list of all the elements of l that do not satisfy f. The order of the elements in the input list is preserved.
Sourceval partition_map : ('a->('b, 'c)Either.t)->'a list->'b list * 'c list
partition_map f l returns a pair of lists (l1, l2) such that, for each element x of the input list l:
if f x is Left y1, then y1 is in l1, and
if f x is Right y2, then y2 is in l2.
The output elements are included in l1 and l2 in the same relative order as the corresponding input elements in l.
In particular, partition_map (fun x -> if f x then Left x else Right x) l is equivalent to partition f l.
assoc a l returns the value associated with key a in the list of pairs l. That is, assoc a [ ...; (a,b); ...] = b if (a,b) is the leftmost binding of a in list l.
assoc_opt a l returns the value associated with key a in the list of pairs l. That is, assoc_opt a [ ...; (a,b); ...] = Some b if (a,b) is the leftmost binding of a in list l. Returns None if there is no value associated with a in the list l.
Sort a list in increasing order according to a comparison function. The comparison function must return 0 if its arguments compare as equal, a positive integer if the first is greater, and a negative integer if the first is smaller (see Array.sort for a complete specification). For example, Stdlib.compare is a suitable comparison function. The resulting list is sorted in increasing order. sort is guaranteed to run in constant heap space (in addition to the size of the result list) and logarithmic stack space.
The current implementation uses Merge Sort. It runs in constant heap space and logarithmic stack space.
Sourceval stable_sort : ('a->'a-> int)->'a list->'a list
Same as sort, but the sorting algorithm is guaranteed to be stable (i.e. elements that compare equal are kept in their original order).
The current implementation uses Merge Sort. It runs in constant heap space and logarithmic stack space.
Sourceval fast_sort : ('a->'a-> int)->'a list->'a list
Same as sort or stable_sort, whichever is faster on typical input.
Sourceval sort_uniq : ('a->'a-> int)->'a list->'a list
Sourceval merge : ('a->'a-> int)->'a list->'a list->'a list
Merge two lists: Assuming that l1 and l2 are sorted according to the comparison function cmp, merge cmp l1 l2 will return a sorted list containing all the elements of l1 and l2. If several elements compare equal, the elements of l1 will be before the elements of l2. Not tail-recursive (sum of the lengths of the arguments).