Values of type
'a Gen.t represent a possibly infinite sequence of values of type 'a. One can only iterate once on the sequence, as it is consumed by iteration/deconstruction/access.
None is returned when the generator is exhausted.
Restart provides utilities to work with restartable generators, that is, functions
unit -> 'a Gen.t that allow to build as many generators from the same source as needed.
A generator may be called several times, yielding the next value each time. It returns
None when no elements remain
type 'a gen = 'a t
module type S = Gen_intf.S
val get : 'a t -> 'a option
Get the next value
val get_exn : 'a t -> 'a
Get the next value, or fails
val junk : 'a t -> unit
Drop the next value, discarding it.
val repeatedly : ( unit -> 'a ) -> 'a t
Call the same function an infinite number of times (useful for instance if the function is a random generator).
Operations on transient generators
val empty : 'a gen
Empty generator, with no elements
val singleton : 'a -> 'a gen
val repeat : 'a -> 'a gen
Repeat same element endlessly
val iterate : 'a -> ( 'a -> 'a ) -> 'a gen
iterate x f is
[x; f x; f (f x); f (f (f x)); ...]
val unfold : ( 'b -> ('a * 'b) option ) -> 'b -> 'a gen
fold, with a deconstructing operation. It keeps on unfolding the
'b value into a new
'b, and a
'a which is yielded, until
None is returned.
val init : ?limit:int -> ( int -> 'a ) -> 'a gen
Calls the function, starting from 0, on increasing indices. If
limit is provided and is a positive int, iteration will stop at the limit (excluded). For instance
init ~limit:4 id will yield 0, 1, 2, and 3.
Note: those combinators, applied to generators (not restartable generators) consume their argument. Sometimes they consume it lazily, sometimes eagerly, but in any case once
f gen has been called (with
f a combinator),
gen shouldn't be used anymore.
val is_empty : _ gen -> bool
Check whether the gen is empty. Pops an element, if any
val fold : ( 'b -> 'a -> 'b ) -> 'b -> 'a gen -> 'b
Fold on the generator, tail-recursively. Consumes the generator.
val reduce : ( 'a -> 'a -> 'a ) -> 'a gen -> 'a
Fold on non-empty sequences. Consumes the generator.
fold, but keeping successive values of the accumulator. Consumes the generator.
val iter : ( 'a -> unit ) -> 'a gen -> unit
Iterate on the gen, consumes it.
val iteri : ( int -> 'a -> unit ) -> 'a gen -> unit
Iterate on elements with their index in the gen, from 0, consuming it.
val length : _ gen -> int
Length of an gen (linear time), consuming it
Lazy map. No iteration is performed now, the function will be called when the result is traversed.
Lazy map with indexing starting from 0. No iteration is performed now, the function will be called when the result is traversed.
Lazy fold and map. No iteration is performed now, the function will be called when the result is traversed. The result is an iterator over the successive states of the fold.
Append the two gens; the result contains the elements of the first, then the elements of the second gen.
Monadic bind; each element is transformed to a sub-gen which is then iterated on, before the next element is processed, and so on.
val mem : ?eq:( 'a -> 'a -> bool ) -> 'a -> 'a gen -> bool
Is the given element, member of the gen?
val nth : int -> 'a gen -> 'a
n-th element, or Not_found
take_nth n g returns every element of
g whose index is a multiple of
n. For instance
take_nth 2 (1--10) |> to_list will return
Filter out elements that do not satisfy the predicate.
Take elements while they satisfy the predicate. The initial generator itself is not to be used anymore after this.
val fold_while : ( 'a -> 'b -> 'a * [ `Stop | `Continue ] ) -> 'a -> 'b gen -> 'a
Fold elements until (
'a, `Stop) is indicated by the accumulator.
Drop elements while they satisfy the predicate. The initial generator itself should not be used anymore, only the result of
Maps some elements to 'b, drop the other ones
partition p l returns the elements that satisfy
p, and the elements that do not satisfy
val for_all : ( 'a -> bool ) -> 'a gen -> bool
Is the predicate true for all elements?
val exists : ( 'a -> bool ) -> 'a gen -> bool
Is the predicate true for at least one element?
val min : ?lt:( 'a -> 'a -> bool ) -> 'a gen -> 'a
Minimum element, according to the given comparison function.
Lexicographic comparison of generators. If a generator is a prefix of the other one, it is considered smaller.
val find : ( 'a -> bool ) -> 'a gen -> 'a option
find p e returns the first element of
e to satisfy
p, or None.
val sum : int gen -> int
Sum of all elements
Map on the two sequences. Stops once one of them is exhausted.
Iterate on the two sequences. Stops once one of them is exhausted.
Fold the common prefix of the two iterators
Succeeds if all pairs of elements satisfy the predicate. Ignores elements of an iterator if the other runs dry.
Succeeds if some pair of elements satisfy the predicate. Ignores elements of an iterator if the other runs dry.
Combine common part of the gens (stops when one is exhausted)
Pick elements fairly in each sub-generator. The merge of gens
e1, e2, ... picks elements in
e2 .... Once a generator is empty, it is skipped; when they are all empty, and none remains in the input, their merge is also empty. For instance,
merge [1;3;5] [2;4;6] will be, in disorder,
Intersection of two sorted sequences. Only elements that occur in both inputs appear in the output
Merge two sorted sequences into a sorted sequence
Sorted merge of multiple sorted sequences
Duplicate the gen into
n generators (default 2). The generators share the same underlying instance of the gen, so the optimal case is when they are consumed evenly
Split the gen into
n generators in a fair way. Elements with
index = k mod n with go to the k-th gen.
n default value is 2.
interleave a b yields an element of
a, then an element of
b, and so on. When a generator is exhausted, this behaves like the other generator.
Put the separator element between all elements of the given gen
Cartesian product, in no predictable order. Works even if some of the arguments are infinite.
Group equal consecutive elements together.
Remove consecutive duplicate elements. Basically this is like
fun e -> map List.hd (group e).
Sort according to the given comparison function. The gen must be finite.
Sort and remove duplicates. The gen must be finite.
chunks n e returns a generator of arrays of length
n, composed of successive elements of
e. The last array may be smaller than
Combinations of given length. The ordering of the elements within each combination is unspecified. Example (ignoring ordering):
combinations 2 (1--3) |> to_list = [[1;2]; [1;3]; [2;3]]
All subsets of the gen (in no particular order). The ordering of the elements within each subset is unspecified.
val of_list : 'a list -> 'a gen
Enumerate elements of the list
val to_list : 'a gen -> 'a list
non tail-call trasnformation to list, in the same order
val to_rev_list : 'a gen -> 'a list
Tail call conversion to list, in reverse order (more efficient)
val to_array : 'a gen -> 'a array
Convert the gen to an array (not very efficient)
val of_array : ?start:int -> ?len:int -> 'a array -> 'a gen
Iterate on (a slice of) the given array
val of_string : ?start:int -> ?len:int -> string -> char gen
Iterate on bytes of the string
val to_string : char gen -> string
Convert into a string
val rand_int : int -> int gen
Random ints in the given range.
val int_range : ?step:int -> int -> int -> int gen
int_range ~step a b generates integers between
b, included, with steps of length
step (1 if omitted).
a is assumed to be smaller than
b, otherwise the result will be empty.
module Infix : sig ... end
val (--) : int -> int -> int gen
val pp : ?start:string -> ?stop:string -> ?sep:string -> ?horizontal:bool -> ( Format.formatter -> 'a -> unit ) -> Format.formatter -> 'a gen -> unit
Pretty print the content of the generator on a formatter.
A restartable generator is a function that produces copies of the same generator, on demand. It has the type
unit -> 'a gen and it is assumed that every generated returned by the function behaves the same (that is, that it traverses the same sequence of elements).
module Restart : sig ... end
Store content of the transient generator in memory, to be able to iterate on it several times later. If possible, consider using combinators from
Restart directly instead.
persistent_lazy, but returns a standard Seq.
peek g transforms the generator
g into a generator of
x, Some next if
x was followed by
x, None if
x was the last element of
peek_n n g iterates on
g, returning along with each element the array of the (at most)
n elements that follow it immediately
Create a new transient generator.
start gen is the same as
gen () but is included for readability.
Very basic interface to manipulate files as sequence of chunks/lines.
module IO : sig ... end