N:bignum
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math::bignum - Arbitrary precision integer numbers
Contents |
SYNOPSIS
package require Tcl ?8.4?
package require math::bignum ?3.1?
::math::bignum::fromstr string ?radix?
::math::bignum::tostr bignum ?radix?
::math::bignum::sign bignum
::math::bignum::abs bignum
::math::bignum::cmp a b
::math::bignum::iszero bignum
::math::bignum::lt a b
::math::bignum::le a b
::math::bignum::gt a b
::math::bignum::ge a b
::math::bignum::eq a b
::math::bignum::ne a b
::math::bignum::isodd bignum
::math::bignum::iseven bignum
::math::bignum::add a b
::math::bignum::sub a b
::math::bignum::mul a b
::math::bignum::divqr a b
::math::bignum::div a b
::math::bignum::rem a b
::math::bignum::mod n m
::math::bignum::pow base exp
::math::bignum::powm base exp m
::math::bignum::sqrt bignum
::math::bignum::rand bits
::math::bignum::lshift bignum bits
::math::bignum::rshift bignum bits
::math::bignum::bitand a b
::math::bignum::bitor a b
::math::bignum::bitxor a b
::math::bignum::setbit bignumVar bit
::math::bignum::clearbit bignumVar bit
::math::bignum::testbit bignum bit
::math::bignum::bits bignum
DESCRIPTION
The bignum package provides arbitrary precision integer math (also known as "big numbers") capabilities to the
Tcl language. Big numbers are internally represented at Tcl lists: this package provides a set of procedures
operating against the internal representation in order to:
� perform math operations
� convert bignums from the internal representation to a string in the desired radix and vice versa. But the
two constants "0" and "1" are automatically converted to the internal representation, in order to easily
compare a number to zero, or increment a big number.
The bignum interface is opaque, so operations on bignums that are not returned by procedures in this package (but
created by hand) may lead to unspecified behaviours. It's safe to treat bignums as pure values, so there is no
need to free a bignum, or to duplicate it via a special operation.
EXAMPLES
This section shows some simple example. This library being just a way to perform math operations, examples may be
the simplest way to learn how to work with it. Consult the API section of this man page for information about
individual procedures.
package require math::bignum
# Multiplication of two bignums
set a [::math::bignum::fromstr 88888881111111]
set b [::math::bignum::fromstr 22222220000000]
set c [::math::bignum::mul $a $b]
puts [::math::bignum::tostr $c] ; # => will output 1975308271604953086420000000
set c [::math::bignum::sqrt $c]
puts [::math::bignum::tostr $c] ; # => will output 44444440277777
# From/To string conversion in different radix
set a [::math::bignum::fromstr 1100010101010111001001111010111 2]
puts [::math::bignum::tostr $a 16] ; # => will output 62ab93d7
# Factorial example
proc fact n {
# fromstr is not needed for 0 and 1
set z 1
for {set i 2} {$i <= $n} {incr i} {
set z [::math::bignum::mul $z [::math::bignum::fromstr $i]]
}
return $z
}
puts [::math::bignum::tostr [fact 100]]
API
::math::bignum::fromstr string ?radix?
Convert string into a bignum. If radix is omitted or zero, the string is interpreted in hex if prefixed
with 0x, in octal if prefixed with ox, in binary if it's pefixed with bx, as a number in radix 10 other-
wise. If instead the radix argument is specified in the range 2-36, the string is interpreted in the given
radix. Please note that this conversion is not needed for two constants : 0 and 1. (see the example)
::math::bignum::tostr bignum ?radix?
Convert bignum into a string representing the number in the specified radix. If radix is omitted, the
default is 10.
::math::bignum::sign bignum
Return the sign of the bignum. The procedure returns 0 if the number is positive, 1 if it's negative.
::math::bignum::abs bignum
Return the absolute value of the bignum.
::math::bignum::cmp a b
Compare the two bignums a and b, returning 0 if a == b, 1 if a > b, and -1 if a < b.
::math::bignum::iszero bignum
Return true if bignum value is zero, otherwise false is returned.
::math::bignum::lt a b
Return true if a < b, otherwise false is returned.
::math::bignum::le a b
Return true if a <= b, otherwise false is returned.
::math::bignum::gt a b
Return true if a > b, otherwise false is returned.
::math::bignum::ge a b
Return true if a >= b, otherwise false is returned.
::math::bignum::eq a b
Return true if a == b, otherwise false is returned.
::math::bignum::ne a b
Return true if a != b, otherwise false is returned.
::math::bignum::isodd bignum
Return true if bignum is odd.
::math::bignum::iseven bignum
Return true if bignum is even.
::math::bignum::add a b
Return the sum of the two bignums a and b.
::math::bignum::sub a b
Return the difference of the two bignums a and b.
::math::bignum::mul a b
Return the product of the two bignums a and b. The implementation uses Karatsuba multiplication if both
the numbers are bigger than a given threshold, otherwise the direct algorith is used.
::math::bignum::divqr a b
Return a two-elements list containing as first element the quotient of the division between the two
bignums a and b, and the remainder of the division as second element.
::math::bignum::div a b
Return the quotient of the division between the two bignums a and b.
::math::bignum::rem a b
Return the remainder of the division between the two bignums a and b.
::math::bignum::mod n m
Return n modulo m. This operation is called modular reduction.
::math::bignum::pow base exp
Return base raised to the exponent exp.
::math::bignum::powm base exp m
Return base raised to the exponent exp, modulo m. This function is often used in the field of cryptogra-
phy.
::math::bignum::sqrt bignum
Return the integer part of the square root of bignum
::math::bignum::rand bits
Return a random number of at most bits bits. The returned number is internally generated using Tcl's expr
rand() function and is not suitable where an unguessable and cryptographically secure random number is
needed.
::math::bignum::lshift bignum bits
Return the result of left shifting bignum's binary representation of bits positions on the left. This is
equivalent to multiplying by 2^bits but much faster.
::math::bignum::rshift bignum bits
Return the result of right shifting bignum's binary representation of bits positions on the right. This
is equivalent to dividing by 2^bits but much faster.
::math::bignum::bitand a b
Return the result of doing a bitwise AND operation on a and b. The operation is restricted to positive
numbers, including zero. When negative numbers are provided as arguments the result is undefined.
::math::bignum::bitor a b
Return the result of doing a bitwise OR operation on a and b. The operation is restricted to positive num-
bers, including zero. When negative numbers are provided as arguments the result is undefined.
::math::bignum::bitxor a b
Return the result of doing a bitwise XOR operation on a and b. The operation is restricted to positive
numbers, including zero. When negative numbers are provided as arguments the result is undefined.
::math::bignum::setbit bignumVar bit
Set the bit at bit position to 1 in the bignum stored in the variable bignumVar. Bit 0 is the least sig-
nificant.
::math::bignum::clearbit bignumVar bit
Set the bit at bit position to 0 in the bignum stored in the variable bignumVar. Bit 0 is the least sig-
nificant.
::math::bignum::testbit bignum bit
Return true if the bit at the bit position of bignum is on, otherwise false is returned. If bit is out of
range, it is considered as set to zero.
::math::bignum::bits bignum
Return the number of bits needed to represent bignum in radix 2.
KEYWORDS
bignums, math, multiprecision, tcl
COPYRIGHT
Copyright (c) 2004 Salvatore Sanfilippo <antirez at invece dot org>
Copyright (c) 2004 Arjen Markus <arjenmarkus at users dot sourceforge dot net>