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Library
Module
Module type
Parameter
Class
Class type
Library
Module
Module type
Parameter
Class
Class type
include module type of Z with type t = Z.t
For an optimal experience with the ocaml
interactive toplevel, the magic commands are:
#load "zarith.cma";;
#install_printer Z.pp_print;;
Alternatively, using the new Zarith_top
toplevel module, simply:
#require "zarith.top";;
type t = Z.t
Type of integers of arbitrary length.
Raised by conversion functions when the value cannot be represented in the destination type.
val zero : t
The number 0.
val one : t
The number 1.
val minus_one : t
The number -1.
val of_int : int -> t
Converts from a base integer.
val of_int32 : int32 -> t
Converts from a 32-bit (signed) integer.
val of_int64 : int64 -> t
Converts from a 64-bit (signed) integer.
val of_nativeint : nativeint -> t
Converts from a native (signed) integer.
val of_int32_unsigned : int32 -> t
Converts from a 32-bit integer, interpreted as an unsigned integer.
val of_int64_unsigned : int64 -> t
Converts from a 64-bit integer, interpreted as an unsigned integer.
val of_nativeint_unsigned : nativeint -> t
Converts from a native integer, interpreted as an unsigned integer..
val of_float : float -> t
Converts from a floating-point value. The value is truncated (rounded towards zero). Raises Overflow
on infinity and NaN arguments.
val of_string : string -> t
Converts a string to an integer. An optional -
prefix indicates a negative number, while a +
prefix is ignored. An optional prefix 0x
, 0o
, or 0b
(following the optional -
or +
prefix) indicates that the number is, represented, in hexadecimal, octal, or binary, respectively. Otherwise, base 10 is assumed. (Unlike C, a lone 0
prefix does not denote octal.) Raises an Invalid_argument
exception if the string is not a syntactically correct representation of an integer.
val of_substring : string -> pos:int -> len:int -> t
of_substring s ~pos ~len
is the same as of_string (String.sub s
pos len)
val of_string_base : int -> string -> t
Parses a number represented as a string in the specified base, with optional -
or +
prefix. The base must be between 2 and 16.
val of_substring_base : int -> string -> pos:int -> len:int -> t
of_substring_base base s ~pos ~len
is the same as of_string_base
base (String.sub s pos len)
Integer division. The result is truncated towards zero and obeys the rule of signs. Raises Division_by_zero
if the divisor (second argument) is 0.
Integer remainder. Can raise a Division_by_zero
. The result of rem a b
has the sign of a
, and its absolute value is strictly smaller than the absolute value of b
. The result satisfies the equality a = b * div a b + rem a b
.
Computes both the integer quotient and the remainder. div_rem a b
is equal to (div a b, rem a b)
. Raises Division_by_zero
if b = 0
.
Integer division with rounding towards +oo (ceiling). Can raise a Division_by_zero
.
Integer division with rounding towards -oo (floor). Can raise a Division_by_zero
.
Euclidean division and remainder. ediv_rem a b
returns a pair (q, r)
such that a = b * q + r
and 0 <= r < |b|
. Raises Division_by_zero
if b = 0
.
Euclidean division. ediv a b
is equal to fst (ediv_rem a b)
. The result satisfies 0 <= a - b * ediv a b < |b|
. Raises Division_by_zero
if b = 0
.
Euclidean remainder. erem a b
is equal to snd (ediv_rem a b)
. The result satisfies 0 <= erem a b < |b|
and a = b * ediv a b + erem a b
. Raises Division_by_zero
if b = 0
.
divexact a b
divides a
by b
, only producing correct result when the division is exact, i.e., when b
evenly divides a
. It should be faster than general division. Can raise a Division_by_zero
.
divisible a b
returns true
if a
is exactly divisible by b
. Unlike the other division functions, b = 0
is accepted (only 0 is considered divisible by 0).
congruent a b c
returns true
if a
is congruent to b
modulo c
. Unlike the other division functions, c = 0
is accepted (only equal numbers are considered equal congruent 0).
For all bit-level operations, negative numbers are considered in 2's complement representation, starting with a virtual infinite number of 1s.
Shifts to the left. Equivalent to a multiplication by a power of 2. The second argument must be nonnegative.
Shifts to the right. This is an arithmetic shift, equivalent to a division by a power of 2 with rounding towards -oo. The second argument must be nonnegative.
Shifts to the right, rounding towards 0. This is equivalent to a division by a power of 2, with truncation. The second argument must be nonnegative.
val numbits : t -> int
Returns the number of significant bits in the given number. If x
is zero, numbits x
returns 0. Otherwise, numbits x
returns a positive integer n
such that 2^{n-1} <= |x| < 2^n
. Note that numbits
is defined for negative arguments, and that numbits (-x) = numbits x
.
val trailing_zeros : t -> int
Returns the number of trailing 0 bits in the given number. If x
is zero, trailing_zeros x
returns max_int
. Otherwise, trailing_zeros x
returns a nonnegative integer n
which is the largest n
such that 2^n
divides x
evenly. Note that trailing_zeros
is defined for negative arguments, and that trailing_zeros (-x) = trailing_zeros x
.
val testbit : t -> int -> bool
testbit x n
return the value of bit number n
in x
: true
if the bit is 1, false
if the bit is 0. Bits are numbered from 0. Raise Invalid_argument
if n
is negative.
val popcount : t -> int
Counts the number of bits set. Raises Overflow
for negative arguments, as those have an infinite number of bits set.
Counts the number of different bits. Raises Overflow
if the arguments have different signs (in which case the distance is infinite).
Note that, when converting to an integer type that cannot represent the converted value, an Overflow
exception is raised.
val to_int : t -> int
Converts to a signed OCaml int
. Raises an Overflow
if the value does not fit in a signed OCaml int
.
val to_int32 : t -> int32
Converts to a signed 32-bit integer int32
. Raises an Overflow
if the value does not fit in a signed int32
.
val to_int64 : t -> int64
Converts to a signed 64-bit integer int64
. Raises an Overflow
if the value does not fit in a signed int64
.
val to_nativeint : t -> nativeint
Converts to a native signed integer nativeint
. Raises an Overflow
if the value does not fit in a signed nativeint
.
val to_int32_unsigned : t -> int32
Converts to an unsigned 32-bit integer. The result is stored into an OCaml int32
. Beware that most Int32
operations consider int32
to a signed type, not unsigned. Raises an Overflow
if the value is negative or does not fit in an unsigned 32-bit integer.
val to_int64_unsigned : t -> int64
Converts to an unsigned 64-bit integer. The result is stored into an OCaml int64
. Beware that most Int64
operations consider int64
to a signed type, not unsigned. Raises an Overflow
if the value is negative or does not fit in an unsigned 64-bit integer.
val to_nativeint_unsigned : t -> nativeint
Converts to a native unsigned integer. The result is stored into an OCaml nativeint
. Beware that most Nativeint
operations consider nativeint
to a signed type, not unsigned. Raises an Overflow
if the value is negative or does not fit in an unsigned native integer.
val to_float : t -> float
Converts to a floating-point value. This function rounds the given integer according to the current rounding mode of the processor. In default mode, it returns the floating-point number nearest to the given integer, breaking ties by rounding to even.
val to_string : t -> string
Gives a human-readable, decimal string representation of the argument.
val format : string -> t -> string
Gives a string representation of the argument in the specified printf-like format. The general specification has the following form:
% [flags] [width] type
Where the type actually indicates the base:
i
, d
, u
: decimalb
: binaryo
: octalx
: lowercase hexadecimalX
: uppercase hexadecimalSupported flags are:
+
: prefix positive numbers with a +
sign-
: left-justify (default is right justification)0
: pad with zeroes (instead of spaces)#
: alternate formatting (actually, simply output a literal-like prefix: 0x
, 0b
, 0o
)Unlike the classic printf
, all numbers are signed (even hexadecimal ones), there is no precision field, and characters that are not part of the format are simply ignored (and not copied in the output).
val fits_int : t -> bool
Whether the argument fits in an OCaml signed int
.
val fits_int32 : t -> bool
Whether the argument fits in a signed int32
.
val fits_int64 : t -> bool
Whether the argument fits in a signed int64
.
val fits_nativeint : t -> bool
Whether the argument fits in a signed nativeint
.
val fits_int32_unsigned : t -> bool
Whether the argument is non-negative and fits in an unsigned int32
.
val fits_int64_unsigned : t -> bool
Whether the argument is non-negative and fits in an unsigned int64
.
val fits_nativeint_unsigned : t -> bool
Whether the argument is non-negative fits in an unsigned nativeint
.
val print : t -> unit
Prints the argument on the standard output.
val output : Stdlib.out_channel -> t -> unit
Prints the argument on the specified channel. Also intended to be used as %a
format printer in Printf.printf
.
val sprint : unit -> t -> string
To be used as %a
format printer in Printf.sprintf
.
val bprint : Stdlib.Buffer.t -> t -> unit
To be used as %a
format printer in Printf.bprintf
.
val pp_print : Stdlib.Format.formatter -> t -> unit
Prints the argument on the specified formatter. Can be used as %a
format printer in Format.printf
and as argument to #install_printer
in the top-level.
Comparison. compare x y
returns 0 if x
equals y
, -1 if x
is smaller than y
, and 1 if x
is greater than y
.
Note that Pervasive.compare can be used to compare reliably two integers only on OCaml 3.12.1 and later versions.
val sign : t -> int
Returns -1, 0, or 1 when the argument is respectively negative, null, or positive.
val is_even : t -> bool
Returns true if the argument is even (divisible by 2), false if odd.
val is_odd : t -> bool
Returns true if the argument is odd, false if even.
val hash : t -> int
Hashes a number, producing a small integer. The result is consistent with equality: if a
= b
, then hash a
= hash b
. The result is the same as produced by OCaml's generic hash function, Hashtbl.hash
. Together with type Z.t
, the function Z.hash
makes it possible to pass module Z
as argument to the functor Hashtbl.Make
.
val seeded_hash : int -> t -> int
Greatest common divisor. The result is always nonnegative. We have gcd(a,0) = gcd(0,a) = abs(a)
, including gcd(0,0) = 0
.
gcdext u v
returns (g,s,t)
where g
is the greatest common divisor and g=us+vt
. g
is always nonnegative.
Note: the function is based on the GMP mpn_gcdext
function. The exact choice of s
and t
such that g=us+vt
is not specified, as it may vary from a version of GMP to another (it has changed notably in GMP 4.3.0 and 4.3.1).
Least common multiple. The result is always nonnegative. We have lcm(a,0) = lcm(0,a) = 0
.
powm base exp mod
computes base
^exp
modulo mod
. Negative exp
are supported, in which case (base
^-1)^(-exp
) modulo mod
is computed. However, if exp
is negative but base
has no inverse modulo mod
, then a Division_by_zero
is raised.
powm_sec base exp mod
computes base
^exp
modulo mod
. Unlike Z.powm
, this function is designed to take the same time and have the same cache access patterns for any two same-size arguments. Used in cryptographic applications, it provides better resistance to side-channel attacks than Z.powm
. The exponent exp
must be positive, and the modulus mod
must be odd. Otherwise, Invalid_arg
is raised.
invert base mod
returns the inverse of base
modulo mod
. Raises a Division_by_zero
if base
is not invertible modulo mod
.
val probab_prime : t -> int -> int
probab_prime x r
returns 0 if x
is definitely composite, 1 if x
is probably prime, and 2 if x
is definitely prime. The r
argument controls how many Miller-Rabin probabilistic primality tests are performed (5 to 10 is a reasonable value).
Returns the next prime greater than the argument. The result is only prime with very high probability.
remove a b
returns a
after removing all the occurences of the factor b
. Also returns how many occurrences were removed.
val fac : int -> t
fac n
returns the factorial of n
(n!
). Raises an Invaid_argument
if n
is non-positive.
val fac2 : int -> t
fac2 n
returns the double factorial of n
(n!!
). Raises an Invaid_argument
if n
is non-positive.
val facM : int -> int -> t
facM n m
returns the m
-th factorial of n
. Raises an Invaid_argument
if n
or m
is non-positive.
val primorial : int -> t
primorial n
returns the product of all positive prime numbers less than or equal to n
. Raises an Invaid_argument
if n
is non-positive.
bin n k
returns the binomial coefficient n
over k
. Raises an Invaid_argument
if k
is non-positive.
val fib : int -> t
fib n
returns the n
-th Fibonacci number. Raises an Invaid_argument
if n
is non-positive.
val lucnum : int -> t
lucnum n
returns the n
-th Lucas number. Raises an Invaid_argument
if n
is non-positive.
pow base exp
raises base
to the exp
power. exp
must be nonnegative. Note that only exponents fitting in a machine integer are supported, as larger exponents would surely make the result's size overflow the address space.
Returns the square root. The result is truncated (rounded down to an integer). Raises an Invalid_argument
on negative arguments.
Returns the square root truncated, and the remainder. Raises an Invalid_argument
on negative arguments.
root x n
computes the n
-th root of x
. n
must be positive and, if n
is even, then x
must be nonnegative. Otherwise, an Invalid_argument
is raised.
rootrem x n
computes the n
-th root of x
and the remainder x-root**n
. n
must be positive and, if n
is even, then x
must be nonnegative. Otherwise, an Invalid_argument
is raised.
val perfect_power : t -> bool
True if the argument has the form a^b
, with b>1
val perfect_square : t -> bool
True if the argument has the form a^2
.
val log2 : t -> int
Returns the base-2 logarithm of its argument, rounded down to an integer. If x
is positive, log2 x
returns the largest n
such that 2^n <= x
. If x
is negative or zero, log2 x
raise the Invalid_argument
exception.
val log2up : t -> int
Returns the base-2 logarithm of its argument, rounded up to an integer. If x
is positive, log2up x
returns the smallest n
such that x <= 2^n
. If x
is negative or zero, log2up x
raise the Invalid_argument
exception.
val size : t -> int
Returns the number of machine words used to represent the number.
extract a off len
returns a nonnegative number corresponding to bits off
to off
+len
-1 of a
. Negative a
are considered in infinite-length 2's complement representation. Raises an Invalid_argument
if off
is strictly negative, or if len
is negative or null.
signed_extract a off len
extracts bits off
to off
+len
-1 of b
, as extract
does, then sign-extends bit len-1
of the result (that is, bit off + len - 1
of a
). The result is between - 2{^[len]-1}
(included) and 2{^[len]-1}
(excluded), and equal to extract a off len
modulo 2{^len}
. Raises an Invalid_argument
if off
is strictly negative, or if len
is negative or null.
val to_bits : t -> string
Returns a binary representation of the argument. The string result should be interpreted as a sequence of bytes, corresponding to the binary representation of the absolute value of the argument in little endian ordering. The sign is not stored in the string.
val of_bits : string -> t
Constructs a number from a binary string representation. The string is interpreted as a sequence of bytes in little endian order, and the result is always positive. We have the identity: of_bits (to_bits x) = abs x
. However, we can have to_bits (of_bits s) <> s
due to the presence of trailing zeros in s.
random_int bound
returns a random integer between 0 (inclusive) and bound
(exclusive). bound
must be greater than 0.
The source of randomness is the Random
module from the OCaml standard library. The optional rng
argument specifies which random state to use. If omitted, the default random state for the Random
module is used.
Random numbers produced by this function are not cryptographically strong and must not be used in cryptographic or high-security contexts. See Z.random_int_gen
for an alternative.
val random_bits : ?rng:Stdlib.Random.State.t -> int -> t
random_bits nbits
returns a random integer between 0 (inclusive) and 2{^nbits}
(exclusive). nbits
must be nonnegative. This is a more efficient special case of Z.random_int
when the bound is a power of two.
The source of randomness and the rng
optional argument are as described in Z.random_int
.
Random numbers produced by this function are not cryptographically strong and must not be used in cryptographic or high-security contexts. See Z.random_bits_gen
for an alternative.
random_int_gen ~fill bound
returns a random integer between 0 (inclusive) and bound
(exclusive). bound
must be greater than 0.
The fill
parameter is the source of randomness. It is called as fill buf pos len
, and is responsible for drawing len
random bytes and writing them to offsets pos
to pos + len - 1
of the byte array buf
.
Example of use where /dev/random
provides the random bytes: << In_channel.with_open_bin "/dev/random" (fun ic -> Z.random_int_gen ~fill:(really_input ic) bound) >> Example of use where the Cryptokit library provides the random bytes: << Z.random_int_gen ~fill:Cryptokit.Random.secure_rng#bytes bound >>
val random_bits_gen : fill:(bytes -> int -> int -> unit) -> int -> t
random_bits_gen ~fill nbits
returns a random integer between 0 (inclusive) and 2{^nbits}
(exclusive). nbits
must be nonnegative. This is a more efficient special case of Z.random_int_gen
when the bound is a power of two. The fill
parameter is as described in Z.random_int_gen
.
Classic (and less classic) prefix and infix int
operators are redefined on t
.
This makes it easy to typeset expressions. Using OCaml 3.12's local open, you can simply write Z.(~$2 + ~$5 * ~$10)
.
val (~$) : int -> t
Conversion from int
of_int
.
module Compare : sig ... end
val _2 : Z.t
val _5 : Z.t
val _7 : Z.t
val _8 : Z.t
val _10 : Z.t
val _60 : Z.t
val _255 : Z.t
val _3600 : Z.t
val _24x3600 : Z.t
val _7x24x3600 : Z.t
val _365x24x3600 : Z.t
val _10_3 : Z.t
val _10_6 : Z.t
val _10_9 : Z.t
val _10_12 : Z.t
val _10_15 : Z.t
val _10_18 : Z.t
val is_neg : Z.t -> bool
val is_pos : Z.t -> bool
val numbits_mod8 : t -> int
val of_binary : string -> Z.t
val to_binary : int -> Z.t -> string
val print_hex : Stdlib.Format.formatter -> Z.t -> unit