Numbers

标准数值类型

抽象数值类型

Core.Number — Type

  1. Number

Abstract supertype for all number types.

source

Core.Real — Type

  1. Real <: Number

Abstract supertype for all real numbers.

source

Core.AbstractFloat — Type

  1. AbstractFloat <: Real

Abstract supertype for all floating point numbers.

source

Core.Integer — Type

  1. Integer <: Real

Abstract supertype for all integers.

source

Core.Signed — Type

  1. Signed <: Integer

Abstract supertype for all signed integers.

source

Core.Unsigned — Type

  1. Unsigned <: Integer

Abstract supertype for all unsigned integers.

source

Base.AbstractIrrational — Type

  1. AbstractIrrational <: Real

Number type representing an exact irrational value.

source

具象数值类型

Core.Float16 — Type

  1. Float16 <: AbstractFloat

16-bit floating point number type.

source

Core.Float32 — Type

  1. Float32 <: AbstractFloat

32-bit floating point number type.

source

Core.Float64 — Type

  1. Float64 <: AbstractFloat

64-bit floating point number type.

source

Base.MPFR.BigFloat — Type

  1. BigFloat <: AbstractFloat

Arbitrary precision floating point number type.

source

Core.Bool — Type

  1. Bool <: Integer

Boolean type, containing the values true and false.

source

Core.Int8 — Type

  1. Int8 <: Signed

8-bit signed integer type.

source

Core.UInt8 — Type

  1. UInt8 <: Unsigned

8-bit unsigned integer type.

source

Core.Int16 — Type

  1. Int16 <: Signed

16-bit signed integer type.

source

Core.UInt16 — Type

  1. UInt16 <: Unsigned

16-bit unsigned integer type.

source

Core.Int32 — Type

  1. Int32 <: Signed

32-bit signed integer type.

source

Core.UInt32 — Type

  1. UInt32 <: Unsigned

32-bit unsigned integer type.

source

Core.Int64 — Type

  1. Int64 <: Signed

64-bit signed integer type.

source

Core.UInt64 — Type

  1. UInt64 <: Unsigned

64-bit unsigned integer type.

source

Core.Int128 — Type

  1. Int128 <: Signed

128-bit signed integer type.

source

Core.UInt128 — Type

  1. UInt128 <: Unsigned

128-bit unsigned integer type.

source

Base.GMP.BigInt — Type

  1. BigInt <: Signed

Arbitrary precision integer type.

source

Base.Complex — Type

  1. Complex{T<:Real} <: Number

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

ComplexF16, ComplexF32 and ComplexF64 are aliases for Complex{Float16}, Complex{Float32} and Complex{Float64} respectively.

source

Base.Rational — Type

  1. Rational{T<:Integer} <: Real

Rational number type, with numerator and denominator of type T. Rationals are checked for overflow.

source

Base.Irrational — Type

  1. Irrational{sym} <: AbstractIrrational

Number type representing an exact irrational value denoted by the symbol sym.

source

数据格式

Base.digits — Function

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

Return 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 indices, such that n == sum([digits[k]*base^(k-1) for k=1:length(digits)]).

Examples

  1. julia> digits(10, base = 10)
  2. 2-element Array{Int64,1}:
  3. 0
  4. 1
  5. julia> digits(10, base = 2)
  6. 4-element Array{Int64,1}:
  7. 0
  8. 1
  9. 0
  10. 1
  11. julia> digits(10, base = 2, pad = 6)
  12. 6-element Array{Int64,1}:
  13. 0
  14. 1
  15. 0
  16. 1
  17. 0
  18. 0

source

Base.digits! — Function

  1. 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 indices. 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.

Examples

  1. julia> digits!([2,2,2,2], 10, base = 2)
  2. 4-element Array{Int64,1}:
  3. 0
  4. 1
  5. 0
  6. 1
  7. julia> digits!([2,2,2,2,2,2], 10, base = 2)
  8. 6-element Array{Int64,1}:
  9. 0
  10. 1
  11. 0
  12. 1
  13. 0
  14. 0

source

Base.bitstring — Function

  1. bitstring(n)

A string giving the literal bit representation of a number.

Examples

  1. julia> bitstring(4)
  2. "0000000000000000000000000000000000000000000000000000000000000100"
  3. julia> bitstring(2.2)
  4. "0100000000000001100110011001100110011001100110011001100110011010"

source

Base.parse — Function

  1. parse(type, str; base)

Parse a string as a number. For Integer types, a base can be specified (the default is 10). For floating-point types, the string is parsed as a decimal floating-point number. Complex types are parsed from decimal strings of the form "R±Iim" as a Complex(R,I) of the requested type; "i" or "j" can also be used instead of "im", and "R" or "Iim" are also permitted. If the string does not contain a valid number, an error is raised.

Julia 1.1

parse(Bool, str) requires at least Julia 1.1.

Examples

  1. julia> parse(Int, "1234")
  2. 1234
  3. julia> parse(Int, "1234", base = 5)
  4. 194
  5. julia> parse(Int, "afc", base = 16)
  6. 2812
  7. julia> parse(Float64, "1.2e-3")
  8. 0.0012
  9. julia> parse(Complex{Float64}, "3.2e-1 + 4.5im")
  10. 0.32 + 4.5im

source

Base.tryparse — Function

  1. tryparse(type, str; base)

Like parse, but returns either a value of the requested type, or nothing if the string does not contain a valid number.

source

Base.big — Function

  1. 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.

source

Base.signed — Function

  1. signed(x)

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

source

Base.unsigned — Function

  1. 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.

Examples

  1. julia> unsigned(-2)
  2. 0xfffffffffffffffe
  3. julia> unsigned(2)
  4. 0x0000000000000002
  5. julia> signed(unsigned(-2))
  6. -2

source

Base.float — Method

  1. float(x)

Convert a number or array to a floating point data type.

source

Base.Math.significand — Function

  1. 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

  1. julia> significand(15.2)/15.2
  2. 0.125
  3. julia> significand(15.2)*8
  4. 15.2

source

Base.Math.exponent — Function

  1. exponent(x) -> Int

Get the exponent of a normalized floating-point number.

source

Base.complex — Method

  1. complex(r, [i])

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

Examples

  1. julia> complex(7)
  2. 7 + 0im
  3. julia> complex([1, 2, 3])
  4. 3-element Array{Complex{Int64},1}:
  5. 1 + 0im
  6. 2 + 0im
  7. 3 + 0im

source

Base.bswap — Function

  1. bswap(n)

Reverse the byte order of n.

Examples

  1. julia> a = bswap(0x10203040)
  2. 0x40302010
  3. julia> bswap(a)
  4. 0x10203040
  5. julia> string(1, base = 2)
  6. "1"
  7. julia> string(bswap(1), base = 2)
  8. "100000000000000000000000000000000000000000000000000000000"

source

Base.hex2bytes — Function

  1. hex2bytes(s::Union{AbstractString,AbstractVector{UInt8}})

Given a string or array s of ASCII codes for a sequence of hexadecimal digits, returns a Vector{UInt8} of bytes corresponding to the binary representation: each successive pair of hexadecimal digits in s gives the value of one byte in the return vector.

The length of s must be even, and the returned array has half of the length of s. See also hex2bytes! for an in-place version, and bytes2hex for the inverse.

Examples

  1. julia> s = string(12345, base = 16)
  2. "3039"
  3. julia> hex2bytes(s)
  4. 2-element Array{UInt8,1}:
  5. 0x30
  6. 0x39
  7. julia> a = b"01abEF"
  8. 6-element Base.CodeUnits{UInt8,String}:
  9. 0x30
  10. 0x31
  11. 0x61
  12. 0x62
  13. 0x45
  14. 0x46
  15. julia> hex2bytes(a)
  16. 3-element Array{UInt8,1}:
  17. 0x01
  18. 0xab
  19. 0xef

source

Base.hex2bytes! — Function

  1. hex2bytes!(d::AbstractVector{UInt8}, s::Union{String,AbstractVector{UInt8}})

Convert an array s of bytes representing a hexadecimal string to its binary representation, similar to hex2bytes except that the output is written in-place in d. The length of s must be exactly twice the length of d.

source

Base.bytes2hex — Function

  1. bytes2hex(a::AbstractArray{UInt8}) -> String
  2. bytes2hex(io::IO, a::AbstractArray{UInt8})

Convert an array a of bytes to its hexadecimal string representation, either returning a String via bytes2hex(a) or writing the string to an io stream via bytes2hex(io, a). The hexadecimal characters are all lowercase.

Examples

  1. julia> a = string(12345, base = 16)
  2. "3039"
  3. julia> b = hex2bytes(a)
  4. 2-element Array{UInt8,1}:
  5. 0x30
  6. 0x39
  7. julia> bytes2hex(b)
  8. "3039"

source

常用数值函数和常量

Base.one — Function

  1. one(x)
  2. 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.

Examples

  1. julia> one(3.7)
  2. 1.0
  3. julia> one(Int)
  4. 1
  5. julia> import Dates; one(Dates.Day(1))
  6. 1

source

Base.oneunit — Function

  1. oneunit(x::T)
  2. 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).

Examples

  1. julia> oneunit(3.7)
  2. 1.0
  3. julia> import Dates; oneunit(Dates.Day)
  4. 1 day

source

Base.zero — Function

  1. zero(x)

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

Examples

  1. julia> zero(1)
  2. 0
  3. julia> zero(big"2.0")
  4. 0.0
  5. julia> zero(rand(2,2))
  6. 2×2 Array{Float64,2}:
  7. 0.0 0.0
  8. 0.0 0.0

source

Base.im — Constant

  1. im

The imaginary unit.

Examples

  1. julia> im * im
  2. -1 + 0im

source

Base.MathConstants.pi — Constant

  1. π
  2. pi

The constant pi.

Examples

  1. julia> pi
  2. π = 3.1415926535897...

source

Base.MathConstants.ℯ — Constant

  1. e

The constant ℯ.

Examples

  1. julia>
  2. = 2.7182818284590...

source

Base.MathConstants.catalan — Constant

  1. catalan

Catalan’s constant.

Examples

  1. julia> Base.MathConstants.catalan
  2. catalan = 0.9159655941772...

source

Base.MathConstants.eulergamma — Constant

  1. γ
  2. eulergamma

Euler’s constant.

Examples

  1. julia> Base.MathConstants.eulergamma
  2. γ = 0.5772156649015...

source

Base.MathConstants.golden — Constant

  1. φ
  2. golden

The golden ratio.

Examples

  1. julia> Base.MathConstants.golden
  2. φ = 1.6180339887498...

source

Base.Inf — Constant

  1. Inf, Inf64

Positive infinity of type Float64.

source

Base.Inf32 — Constant

  1. Inf32

Positive infinity of type Float32.

source

Base.Inf16 — Constant

  1. Inf16

Positive infinity of type Float16.

source

Base.NaN — Constant

  1. NaN, NaN64

A not-a-number value of type Float64.

source

Base.NaN32 — Constant

  1. NaN32

A not-a-number value of type Float32.

source

Base.NaN16 — Constant

  1. NaN16

A not-a-number value of type Float16.

source

Base.issubnormal — Function

  1. issubnormal(f) -> Bool

Test whether a floating point number is subnormal.

source

Base.isfinite — Function

  1. isfinite(f) -> Bool

Test whether a number is finite.

Examples

  1. julia> isfinite(5)
  2. true
  3. julia> isfinite(NaN32)
  4. false

source

Base.isinf — Function

  1. isinf(f) -> Bool

Test whether a number is infinite.

source

Base.isnan — Function

  1. isnan(f) -> Bool

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

source

Base.iszero — Function

  1. iszero(x)

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

Examples

  1. julia> iszero(0.0)
  2. true
  3. julia> iszero([1, 9, 0])
  4. false
  5. julia> iszero([false, 0, 0])
  6. true

source

Base.isone — Function

  1. isone(x)

Return true if x == one(x); if x is an array, this checks whether x is an identity matrix.

Examples

  1. julia> isone(1.0)
  2. true
  3. julia> isone([1 0; 0 2])
  4. false
  5. julia> isone([1 0; 0 true])
  6. true

source

Base.nextfloat — Function

  1. 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.

source

  1. nextfloat(x::AbstractFloat)

Return 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 return x.

source

Base.prevfloat — Function

  1. prevfloat(x::AbstractFloat, n::Integer)

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

source

  1. prevfloat(x::AbstractFloat)

Return 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 return x.

source

Base.isinteger — Function

  1. isinteger(x) -> Bool

Test whether x is numerically equal to some integer.

Examples

  1. julia> isinteger(4.0)
  2. true

source

Base.isreal — Function

  1. isreal(x) -> Bool

Test whether x or all its elements are numerically equal to some real number including infinities and NaNs. isreal(x) is true if isequal(x, real(x)) is true.

Examples

  1. julia> isreal(5.)
  2. true
  3. julia> isreal(Inf + 0im)
  4. true
  5. julia> isreal([4.; complex(0,1)])
  6. false

source

Core.Float32 — Method

  1. Float32(x [, mode::RoundingMode])

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

Examples

  1. julia> Float32(1/3, RoundDown)
  2. 0.3333333f0
  3. julia> Float32(1/3, RoundUp)
  4. 0.33333334f0

See RoundingMode for available rounding modes.

source

Core.Float64 — Method

  1. Float64(x [, mode::RoundingMode])

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

Examples

  1. julia> Float64(pi, RoundDown)
  2. 3.141592653589793
  3. julia> Float64(pi, RoundUp)
  4. 3.1415926535897936

See RoundingMode for available rounding modes.

source

Base.Rounding.rounding — Function

  1. 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.

source

Base.Rounding.setrounding — Method

  1. 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 is currently only supported for T == BigFloat.

Warning

This function is not thread-safe. It will affect code running on all threads, but its behavior is undefined if called concurrently with computations that use the setting.

source

Base.Rounding.setrounding — Method

  1. setrounding(f::Function, T, mode)

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

  1. old = rounding(T)
  2. setrounding(T, mode)
  3. f()
  4. setrounding(T, old)

See RoundingMode for available rounding modes.

source

Base.Rounding.get_zero_subnormals — Function

  1. get_zero_subnormals() -> Bool

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

Warning

This function only affects the current thread.

source

Base.Rounding.set_zero_subnormals — Function

  1. 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).

Warning

This function only affects the current thread.

source

整型

Base.count_ones — Function

  1. count_ones(x::Integer) -> Integer

Number of ones in the binary representation of x.

Examples

  1. julia> count_ones(7)
  2. 3

source

Base.count_zeros — Function

  1. count_zeros(x::Integer) -> Integer

Number of zeros in the binary representation of x.

Examples

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

source

Base.leading_zeros — Function

  1. leading_zeros(x::Integer) -> Integer

Number of zeros leading the binary representation of x.

Examples

  1. julia> leading_zeros(Int32(1))
  2. 31

source

Base.leading_ones — Function

  1. leading_ones(x::Integer) -> Integer

Number of ones leading the binary representation of x.

Examples

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

source

Base.trailing_zeros — Function

  1. trailing_zeros(x::Integer) -> Integer

Number of zeros trailing the binary representation of x.

Examples

  1. julia> trailing_zeros(2)
  2. 1

source

Base.trailing_ones — Function

  1. trailing_ones(x::Integer) -> Integer

Number of ones trailing the binary representation of x.

Examples

  1. julia> trailing_ones(3)
  2. 2

source

Base.isodd — Function

  1. isodd(x::Integer) -> Bool

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

Examples

  1. julia> isodd(9)
  2. true
  3. julia> isodd(10)
  4. false

source

Base.iseven — Function

  1. iseven(x::Integer) -> Bool

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

Examples

  1. julia> iseven(9)
  2. false
  3. julia> iseven(10)
  4. true

source

Core.@int128_str — Macro

  1. @int128_str str
  2. @int128_str(str)

@int128_str parses a string into a Int128 Throws an ArgumentError if the string is not a valid integer

source

Core.@uint128_str — Macro

  1. @uint128_str str
  2. @uint128_str(str)

@uint128_str parses a string into a UInt128 Throws an ArgumentError if the string is not a valid integer

source

BigFloats and BigInts

The BigFloat and BigInt types implements arbitrary-precision floating point and integer arithmetic, respectively. For BigFloat the GNU MPFR library is used, and for BigInt the GNU Multiple Precision Arithmetic Library (GMP) is used.

Base.MPFR.BigFloat — Method

  1. BigFloat(x::Union{Real, AbstractString} [, rounding::RoundingMode=rounding(BigFloat)]; [precision::Integer=precision(BigFloat)])

Create an arbitrary precision floating point number from x, with precision precision. The rounding argument specifies the direction in which the result should be rounded if the conversion cannot be done exactly. If not provided, these are set by the current global values.

BigFloat(x::Real) is the same as convert(BigFloat,x), except if x itself is already BigFloat, in which case it will return a value with the precision set to the current global precision; convert will always return x.

BigFloat(x::AbstractString) is identical to parse. This is provided for convenience since decimal literals are converted to Float64 when parsed, so BigFloat(2.1) may not yield what you expect.

Julia 1.1

precision as a keyword argument requires at least Julia 1.1. In Julia 1.0 precision is the second positional argument (BigFloat(x, precision)).

Examples

  1. julia> BigFloat(2.1) # 2.1 here is a Float64
  2. 2.100000000000000088817841970012523233890533447265625
  3. julia> BigFloat("2.1") # the closest BigFloat to 2.1
  4. 2.099999999999999999999999999999999999999999999999999999999999999999999999999986
  5. julia> BigFloat("2.1", RoundUp)
  6. 2.100000000000000000000000000000000000000000000000000000000000000000000000000021
  7. julia> BigFloat("2.1", RoundUp, precision=128)
  8. 2.100000000000000000000000000000000000007

See also

source

Base.precision — Function

  1. precision(num::AbstractFloat)

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

source

Base.precision — Method

  1. precision(BigFloat)

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

source

Base.MPFR.setprecision — Function

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

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

Warning

This function is not thread-safe. It will affect code running on all threads, but its behavior is undefined if called concurrently with computations that use the setting.

source

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

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

  1. old = precision(BigFloat)
  2. setprecision(BigFloat, precision)
  3. f()
  4. setprecision(BigFloat, old)

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

Note: nextfloat(), prevfloat() do not use the precision mentioned by setprecision

source

Base.GMP.BigInt — Method

  1. 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.

Examples

  1. julia> parse(BigInt, "42")
  2. 42
  3. julia> big"313"
  4. 313

source

Core.@big_str — Macro

  1. @big_str str
  2. @big_str(str)

Parse a string into a BigInt or BigFloat, and throw an ArgumentError if the string is not a valid number. For integers _ is allowed in the string as a separator.

Examples

  1. julia> big"123_456"
  2. 123456
  3. julia> big"7891.5"
  4. 7891.5

source