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/Julia 0.6

Numbers

Standard Numeric Types

Abstract number types

Core.NumberType

Number

Abstract supertype for all number types.

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Core.RealType

Real <: Number

Abstract supertype for all real numbers.

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Core.AbstractFloatType

AbstractFloat <: Real

Abstract supertype for all floating point numbers.

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Core.IntegerType

Integer <: Real

Abstract supertype for all integers.

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Core.SignedType

Signed <: Integer

Abstract supertype for all signed integers.

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Core.UnsignedType

Unsigned <: Integer

Abstract supertype for all unsigned integers.

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Concrete number types

Core.Float16Type

Float16 <: AbstractFloat

16-bit floating point number type.

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Core.Float32Type

Float32 <: AbstractFloat

32-bit floating point number type.

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Core.Float64Type

Float64 <: AbstractFloat

64-bit floating point number type.

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Base.MPFR.BigFloatType

BigFloat <: AbstractFloat

Arbitrary precision floating point number type.

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Core.BoolType

Bool <: Integer

Boolean type.

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Core.Int8Type

Int8 <: Signed

8-bit signed integer type.

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Core.UInt8Type

UInt8 <: Unsigned

8-bit unsigned integer type.

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Core.Int16Type

Int16 <: Signed

16-bit signed integer type.

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Core.UInt16Type

UInt16 <: Unsigned

16-bit unsigned integer type.

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Core.Int32Type

Int32 <: Signed

32-bit signed integer type.

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Core.UInt32Type

UInt32 <: Unsigned

32-bit unsigned integer type.

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Core.Int64Type

Int64 <: Signed

64-bit signed integer type.

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Core.UInt64Type

UInt64 <: Unsigned

64-bit unsigned integer type.

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Core.Int128Type

Int128 <: Signed

128-bit signed integer type.

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Core.UInt128Type

UInt128 <: Unsigned

128-bit unsigned integer type.

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Base.GMP.BigIntType

BigInt <: Integer

Arbitrary precision integer type.

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Base.ComplexType

Complex{T<:Real} <: Number

Complex number type with real and imaginary part of type T.

Complex32, Complex64 and Complex128 are aliases for Complex{Float16}, Complex{Float32} and Complex{Float64} respectively.

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Base.RationalType

Rational{T<:Integer} <: Real

Rational number type, with numerator and denominator of type T.

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Base.IrrationalType

Irrational <: Real

Irrational number type.

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Data Formats

Base.binFunction

bin(n, pad::Int=1)

Convert an integer to a binary string, optionally specifying a number of digits to pad to.

julia> bin(10,2)
"1010"

julia> bin(10,8)
"00001010"
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Base.hexFunction

hex(n, pad::Int=1)

Convert an integer to a hexadecimal string, optionally specifying a number of digits to pad to.

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Base.decFunction

dec(n, pad::Int=1)

Convert an integer to a decimal string, optionally specifying a number of digits to pad to.

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Base.octFunction

oct(n, pad::Int=1)

Convert an integer to an octal string, optionally specifying a number of digits to pad to.

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Base.baseFunction

base(base::Integer, n::Integer, pad::Integer=1)

Convert an integer n to a string in the given base, optionally specifying a number of digits to pad to.

julia> base(13,5,4)
"0005"

julia> base(5,13,4)
"0023"
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Base.digitsFunction

digits([T<:Integer], n::Integer, base::T=10, pad::Integer=1)

Returns an array with element type T (default Int) of the digits of n in the given base, optionally padded with zeros to a specified size. More significant digits are at higher indexes, such that n == sum([digits[k]*base^(k-1) for k=1:length(digits)]).

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Base.digits!Function

digits!(array, n::Integer, base::Integer=10)

Fills an array of the digits of n in the given base. More significant digits are at higher indexes. If the array length is insufficient, the least significant digits are filled up to the array length. If the array length is excessive, the excess portion is filled with zeros.

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Base.bitsFunction

bits(n)

A string giving the literal bit representation of a number.

julia> bits(4)
"0000000000000000000000000000000000000000000000000000000000000100"

julia> bits(2.2)
"0100000000000001100110011001100110011001100110011001100110011010"
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Base.parseMethod

parse(type, str, [base])

Parse a string as a number. If the type is an integer type, then a base can be specified (the default is 10). If the type is a floating point type, the string is parsed as a decimal floating point number. If the string does not contain a valid number, an error is raised.

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Base.tryparseFunction

tryparse(type, str, [base])

Like parse, but returns a Nullable of the requested type. The result will be null if the string does not contain a valid number.

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Base.bigFunction

big(x)

Convert a number to a maximum precision representation (typically BigInt or BigFloat). See BigFloat for information about some pitfalls with floating-point numbers.

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Base.signedFunction

signed(x)

Convert a number to a signed integer. If the argument is unsigned, it is reinterpreted as signed without checking for overflow.

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Base.unsignedFunction

unsigned(x) -> Unsigned

Convert a number to an unsigned integer. If the argument is signed, it is reinterpreted as unsigned without checking for negative values.

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Base.floatMethod

float(x)

Convert a number or array to a floating point data type. When passed a string, this function is equivalent to parse(Float64, x).

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Base.Math.significandFunction

significand(x)

Extract the significand(s) (a.k.a. mantissa), in binary representation, of a floating-point number. If x is a non-zero finite number, then the result will be a number of the same type on the interval $[1,2)$. Otherwise x is returned.

Examples

julia> significand(15.2)/15.2
0.125

julia> significand(15.2)*8
15.2
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Base.Math.exponentFunction

exponent(x) -> Int

Get the exponent of a normalized floating-point number.

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Base.complexMethod

complex(r, [i])

Convert real numbers or arrays to complex. i defaults to zero.

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Base.bswapFunction

bswap(n)

Byte-swap an integer. Flip the bits of its binary representation.

julia> a = bswap(4)
288230376151711744

julia> bswap(a)
4

julia> bin(1)
"1"

julia> bin(bswap(1))
"100000000000000000000000000000000000000000000000000000000"
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Base.num2hexFunction

num2hex(f)

Get a hexadecimal string of the binary representation of a floating point number.

julia> num2hex(2.2)
"400199999999999a"
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Base.hex2numFunction

hex2num(str)

Convert a hexadecimal string to the floating point number it represents.

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Base.hex2bytesFunction

hex2bytes(s::AbstractString)

Convert an arbitrarily long hexadecimal string to its binary representation. Returns an Array{UInt8,1}, i.e. an array of bytes.

julia> a = hex(12345)
"3039"

julia> hex2bytes(a)
2-element Array{UInt8,1}:
 0x30
 0x39
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Base.bytes2hexFunction

bytes2hex(bin_arr::Array{UInt8, 1}) -> String

Convert an array of bytes to its hexadecimal representation. All characters are in lower-case.

julia> a = hex(12345)
"3039"

julia> b = hex2bytes(a)
2-element Array{UInt8,1}:
 0x30
 0x39

julia> bytes2hex(b)
"3039"
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General Number Functions and Constants

Base.oneFunction

one(x)
one(T::type)

Return a multiplicative identity for x: a value such that one(x)*x == x*one(x) == x. Alternatively one(T) can take a type T, in which case one returns a multiplicative identity for any x of type T.

If possible, one(x) returns a value of the same type as x, and one(T) returns a value of type T. However, this may not be the case for types representing dimensionful quantities (e.g. time in days), since the multiplicative identity must be dimensionless. In that case, one(x) should return an identity value of the same precision (and shape, for matrices) as x.

If you want a quantity that is of the same type as x, or of type T, even if x is dimensionful, use oneunit instead.

julia> one(3.7)
1.0

julia> one(Int)
1

julia> one(Dates.Day(1))
1
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Base.oneunitFunction

oneunit(x::T)
oneunit(T::Type)

Returns T(one(x)), where T is either the type of the argument or (if a type is passed) the argument. This differs from one for dimensionful quantities: one is dimensionless (a multiplicative identity) while oneunit is dimensionful (of the same type as x, or of type T).

julia> oneunit(3.7)
1.0

julia> oneunit(Dates.Day)
1 day
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Base.zeroFunction

zero(x)

Get the additive identity element for the type of x (x can also specify the type itself).

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Base.piConstant

pi
π

The constant pi.

julia> pi
π = 3.1415926535897...
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Base.imConstant

im

The imaginary unit.

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Base.euConstant

e
eu

The constant e.

julia> e
e = 2.7182818284590...
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Base.catalanConstant

catalan

Catalan's constant.

julia> catalan
catalan = 0.9159655941772...
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Base.eulergammaConstant

γ
eulergamma

Euler's constant.

julia> eulergamma
γ = 0.5772156649015...
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Base.goldenConstant

φ
golden

The golden ratio.

julia> golden
φ = 1.6180339887498...
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Base.InfConstant

Inf

Positive infinity of type Float64.

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Base.Inf32Constant

Inf32

Positive infinity of type Float32.

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Base.Inf16Constant

Inf16

Positive infinity of type Float16.

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Base.NaNConstant

NaN

A not-a-number value of type Float64.

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Base.NaN32Constant

NaN32

A not-a-number value of type Float32.

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Base.NaN16Constant

NaN16

A not-a-number value of type Float16.

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Base.issubnormalFunction

issubnormal(f) -> Bool

Test whether a floating point number is subnormal.

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Base.isfiniteFunction

isfinite(f) -> Bool

Test whether a number is finite.

julia> isfinite(5)
true

julia> isfinite(NaN32)
false
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Base.isinfFunction

isinf(f) -> Bool

Test whether a number is infinite.

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Base.isnanFunction

isnan(f) -> Bool

Test whether a floating point number is not a number (NaN).

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Base.iszeroFunction

iszero(x)

Return true if x == zero(x); if x is an array, this checks whether all of the elements of x are zero.

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Base.nextfloatFunction

nextfloat(x::AbstractFloat, n::Integer)

The result of n iterative applications of nextfloat to x if n >= 0, or -n applications of prevfloat if n < 0.

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nextfloat(x::AbstractFloat)

Returns the smallest floating point number y of the same type as x such x < y. If no such y exists (e.g. if x is Inf or NaN), then returns x.

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Base.prevfloatFunction

prevfloat(x::AbstractFloat)

Returns the largest floating point number y of the same type as x such y < x. If no such y exists (e.g. if x is -Inf or NaN), then returns x.

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Base.isintegerFunction

isinteger(x) -> Bool

Test whether x is numerically equal to some integer.

julia> isinteger(4.0)
true
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Base.isrealFunction

isreal(x) -> Bool

Test whether x or all its elements are numerically equal to some real number.

julia> isreal(5.)
true

julia> isreal([4.; complex(0,1)])
false
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Core.Float32Method

Float32(x [, mode::RoundingMode])

Create a Float32 from x. If x is not exactly representable then mode determines how x is rounded.

julia> Float32(1/3, RoundDown)
0.3333333f0

julia> Float32(1/3, RoundUp)
0.33333334f0

See RoundingMode for available rounding modes.

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Core.Float64Method

Float64(x [, mode::RoundingMode])

Create a Float64 from x. If x is not exactly representable then mode determines how x is rounded.

julia> Float64(pi, RoundDown)
3.141592653589793

julia> Float64(pi, RoundUp)
3.1415926535897936

See RoundingMode for available rounding modes.

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Base.GMP.BigIntMethod

BigInt(x)

Create an arbitrary precision integer. x may be an Int (or anything that can be converted to an Int). The usual mathematical operators are defined for this type, and results are promoted to a BigInt.

Instances can be constructed from strings via parse, or using the big string literal.

julia> parse(BigInt, "42")
42

julia> big"313"
313
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Base.MPFR.BigFloatMethod

BigFloat(x)

Create an arbitrary precision floating point number. x may be an Integer, a Float64 or a BigInt. The usual mathematical operators are defined for this type, and results are promoted to a BigFloat.

Note that because decimal literals are converted to floating point numbers when parsed, BigFloat(2.1) may not yield what you expect. You may instead prefer to initialize constants from strings via parse, or using the big string literal.

julia> BigFloat(2.1)
2.100000000000000088817841970012523233890533447265625000000000000000000000000000

julia> big"2.1"
2.099999999999999999999999999999999999999999999999999999999999999999999999999986
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Base.Rounding.roundingFunction

rounding(T)

Get the current floating point rounding mode for type T, controlling the rounding of basic arithmetic functions (+, -, *, / and sqrt) and type conversion.

See RoundingMode for available modes.

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Base.Rounding.setroundingMethod

setrounding(T, mode)

Set the rounding mode of floating point type T, controlling the rounding of basic arithmetic functions (+, -, *, / and sqrt) and type conversion. Other numerical functions may give incorrect or invalid values when using rounding modes other than the default RoundNearest.

Note that this may affect other types, for instance changing the rounding mode of Float64 will change the rounding mode of Float32. See RoundingMode for available modes.

Warning

This feature is still experimental, and may give unexpected or incorrect values.

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Base.Rounding.setroundingMethod

setrounding(f::Function, T, mode)

Change the rounding mode of floating point type T for the duration of f. It is logically equivalent to:

old = rounding(T)
setrounding(T, mode)
f()
setrounding(T, old)

See RoundingMode for available rounding modes.

Warning

This feature is still experimental, and may give unexpected or incorrect values. A known problem is the interaction with compiler optimisations, e.g.

julia> setrounding(Float64,RoundDown) do
           1.1 + 0.1
       end
1.2000000000000002

Here the compiler is constant folding, that is evaluating a known constant expression at compile time, however the rounding mode is only changed at runtime, so this is not reflected in the function result. This can be avoided by moving constants outside the expression, e.g.

julia> x = 1.1; y = 0.1;

julia> setrounding(Float64,RoundDown) do
           x + y
       end
1.2
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Base.Rounding.get_zero_subnormalsFunction

get_zero_subnormals() -> Bool

Returns false if operations on subnormal floating-point values ("denormals") obey rules for IEEE arithmetic, and true if they might be converted to zeros.

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Base.Rounding.set_zero_subnormalsFunction

set_zero_subnormals(yes::Bool) -> Bool

If yes is false, subsequent floating-point operations follow rules for IEEE arithmetic on subnormal values ("denormals"). Otherwise, floating-point operations are permitted (but not required) to convert subnormal inputs or outputs to zero. Returns true unless yes==true but the hardware does not support zeroing of subnormal numbers.

set_zero_subnormals(true) can speed up some computations on some hardware. However, it can break identities such as (x-y==0) == (x==y).

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Integers

Base.count_onesFunction

count_ones(x::Integer) -> Integer

Number of ones in the binary representation of x.

julia> count_ones(7)
3
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Base.count_zerosFunction

count_zeros(x::Integer) -> Integer

Number of zeros in the binary representation of x.

julia> count_zeros(Int32(2 ^ 16 - 1))
16
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Base.leading_zerosFunction

leading_zeros(x::Integer) -> Integer

Number of zeros leading the binary representation of x.

julia> leading_zeros(Int32(1))
31
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Base.leading_onesFunction

leading_ones(x::Integer) -> Integer

Number of ones leading the binary representation of x.

julia> leading_ones(UInt32(2 ^ 32 - 2))
31
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Base.trailing_zerosFunction

trailing_zeros(x::Integer) -> Integer

Number of zeros trailing the binary representation of x.

julia> trailing_zeros(2)
1
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Base.trailing_onesFunction

trailing_ones(x::Integer) -> Integer

Number of ones trailing the binary representation of x.

julia> trailing_ones(3)
2
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Base.isoddFunction

isodd(x::Integer) -> Bool

Returns true if x is odd (that is, not divisible by 2), and false otherwise.

julia> isodd(9)
true

julia> isodd(10)
false
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Base.isevenFunction

iseven(x::Integer) -> Bool

Returns true is x is even (that is, divisible by 2), and false otherwise.

julia> iseven(9)
false

julia> iseven(10)
true
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BigFloats

The BigFloat type implements arbitrary-precision floating-point arithmetic using the GNU MPFR library.

Base.precisionFunction

precision(num::AbstractFloat)

Get the precision of a floating point number, as defined by the effective number of bits in the mantissa.

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Base.precisionMethod

precision(BigFloat)

Get the precision (in bits) currently used for BigFloat arithmetic.

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Base.MPFR.setprecisionFunction

setprecision([T=BigFloat,] precision::Int)

Set the precision (in bits) to be used for T arithmetic.

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setprecision(f::Function, [T=BigFloat,] precision::Integer)

Change the T arithmetic precision (in bits) for the duration of f. It is logically equivalent to:

old = precision(BigFloat)
setprecision(BigFloat, precision)
f()
setprecision(BigFloat, old)

Often used as setprecision(T, precision) do ... end

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Base.MPFR.BigFloatMethod

BigFloat(x, prec::Int)

Create a representation of x as a BigFloat with precision prec.

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Base.MPFR.BigFloatMethod

BigFloat(x, rounding::RoundingMode)

Create a representation of x as a BigFloat with the current global precision and rounding mode rounding.

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Base.MPFR.BigFloatMethod

BigFloat(x, prec::Int, rounding::RoundingMode)

Create a representation of x as a BigFloat with precision prec and rounding mode rounding.

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Base.MPFR.BigFloatMethod

BigFloat(x::String)

Create a representation of the string x as a BigFloat.

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Random Numbers

Random number generation in Julia uses the Mersenne Twister library via MersenneTwister objects. Julia has a global RNG, which is used by default. Other RNG types can be plugged in by inheriting the AbstractRNG type; they can then be used to have multiple streams of random numbers. Besides MersenneTwister, Julia also provides the RandomDevice RNG type, which is a wrapper over the OS provided entropy.

Most functions related to random generation accept an optional AbstractRNG as the first argument, rng , which defaults to the global one if not provided. Morever, some of them accept optionally dimension specifications dims... (which can be given as a tuple) to generate arrays of random values.

A MersenneTwister or RandomDevice RNG can generate random numbers of the following types: Float16, Float32, Float64, Bool, Int8, UInt8, Int16, UInt16, Int32, UInt32, Int64, UInt64, Int128, UInt128, BigInt (or complex numbers of those types). Random floating point numbers are generated uniformly in $[0, 1)$. As BigInt represents unbounded integers, the interval must be specified (e.g. rand(big(1:6))).

Base.Random.srandFunction

srand([rng=GLOBAL_RNG], [seed]) -> rng
srand([rng=GLOBAL_RNG], filename, n=4) -> rng

Reseed the random number generator. If a seed is provided, the RNG will give a reproducible sequence of numbers, otherwise Julia will get entropy from the system. For MersenneTwister, the seed may be a non-negative integer, a vector of UInt32 integers or a filename, in which case the seed is read from a file (4n bytes are read from the file, where n is an optional argument). RandomDevice does not support seeding.

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Base.Random.MersenneTwisterType

MersenneTwister(seed)

Create a MersenneTwister RNG object. Different RNG objects can have their own seeds, which may be useful for generating different streams of random numbers.

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Base.Random.RandomDeviceType

RandomDevice()

Create a RandomDevice RNG object. Two such objects will always generate different streams of random numbers.

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Base.Random.randFunction

rand([rng=GLOBAL_RNG], [S], [dims...])

Pick a random element or array of random elements from the set of values specified by S; S can be

  • an indexable collection (for example 1:n or ['x','y','z']), or

  • a type: the set of values to pick from is then equivalent to typemin(S):typemax(S) for integers (this is not applicable to BigInt), and to $[0, 1)$ for floating point numbers;

S defaults to Float64.

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Base.Random.rand!Function

rand!([rng=GLOBAL_RNG], A, [coll])

Populate the array A with random values. If the indexable collection coll is specified, the values are picked randomly from coll. This is equivalent to copy!(A, rand(rng, coll, size(A))) or copy!(A, rand(rng, eltype(A), size(A))) but without allocating a new array.

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Base.Random.bitrandFunction

bitrand([rng=GLOBAL_RNG], [dims...])

Generate a BitArray of random boolean values.

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Base.Random.randnFunction

randn([rng=GLOBAL_RNG], [T=Float64], [dims...])

Generate a normally-distributed random number of type T with mean 0 and standard deviation 1. Optionally generate an array of normally-distributed random numbers. The Base module currently provides an implementation for the types Float16, Float32, and Float64 (the default).

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Base.Random.randn!Function

randn!([rng=GLOBAL_RNG], A::AbstractArray) -> A

Fill the array A with normally-distributed (mean 0, standard deviation 1) random numbers. Also see the rand function.

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Base.Random.randexpFunction

randexp([rng=GLOBAL_RNG], [T=Float64], [dims...])

Generate a random number of type T according to the exponential distribution with scale 1. Optionally generate an array of such random numbers. The Base module currently provides an implementation for the types Float16, Float32, and Float64 (the default).

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Base.Random.randexp!Function

randexp!([rng=GLOBAL_RNG], A::AbstractArray) -> A

Fill the array A with random numbers following the exponential distribution (with scale 1).

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Base.Random.randjumpFunction

randjump(r::MersenneTwister, jumps::Integer, [jumppoly::AbstractString=dSFMT.JPOLY1e21]) -> Vector{MersenneTwister}

Create an array of the size jumps of initialized MersenneTwister RNG objects. The first RNG object given as a parameter and following MersenneTwister RNGs in the array are initialized such that a state of the RNG object in the array would be moved forward (without generating numbers) from a previous RNG object array element on a particular number of steps encoded by the jump polynomial jumppoly.

Default jump polynomial moves forward MersenneTwister RNG state by 10^20 steps.

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© 2009–2016 Jeff Bezanson, Stefan Karpinski, Viral B. Shah, and other contributors
Licensed under the MIT License.
https://docs.julialang.org/en/release-0.6/stdlib/numbers/