Improve documentation for complex (#16588)

* Improve documentation for complex

Add missing doc comments

* Add runnableExample

Add links for principal values
Optimize `-`
Change var to let

* Use std prefix for imports
This commit is contained in:
konsumlamm
2021-01-05 17:50:15 +01:00
committed by GitHub
parent df9e74b510
commit 0c4bd65e8d
2 changed files with 171 additions and 113 deletions

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@@ -7,106 +7,155 @@
# distribution, for details about the copyright.
#
## This module implements complex numbers.
## Complex numbers are currently implemented as generic on a 64-bit or 32-bit float.
## This module implements complex numbers
## and basic mathematical operations on them.
##
## Complex numbers are currently generic over 64-bit or 32-bit floats.
runnableExamples:
from std/math import almostEqual, sqrt
func almostEqual(a, b: Complex): bool =
almostEqual(a.re, b.re) and almostEqual(a.im, b.im)
let
z1 = complex(1.0, 2.0)
z2 = complex(3.0, -4.0)
assert almostEqual(z1 + z2, complex(4.0, -2.0))
assert almostEqual(z1 - z2, complex(-2.0, 6.0))
assert almostEqual(z1 * z2, complex(11.0, 2.0))
assert almostEqual(z1 / z2, complex(-0.2, 0.4))
assert almostEqual(abs(z1), sqrt(5.0))
assert almostEqual(conjugate(z1), complex(1.0, -2.0))
let (r, phi) = z1.polar
assert almostEqual(rect(r, phi), z1)
{.push checks: off, line_dir: off, stack_trace: off, debugger: off.}
# the user does not want to trace a part of the standard library!
import math
import std/math
type
Complex*[T: SomeFloat] = object
re*, im*: T
## A complex number, consisting of a real and an imaginary part.
re*, im*: T
Complex64* = Complex[float64]
## Alias for a pair of 64-bit floats.
## Alias for a complex number using 64-bit floats.
Complex32* = Complex[float32]
## Alias for a pair of 32-bit floats.
## Alias for a complex number using 32-bit floats.
func complex*[T: SomeFloat](re: T; im: T = 0.0): Complex[T] =
## Returns a `Complex[T]` with real part `re` and imaginary part `im`.
result.re = re
result.im = im
func complex32*(re: float32; im: float32 = 0.0): Complex[float32] =
func complex32*(re: float32; im: float32 = 0.0): Complex32 =
## Returns a `Complex32` with real part `re` and imaginary part `im`.
result.re = re
result.im = im
func complex64*(re: float64; im: float64 = 0.0): Complex[float64] =
func complex64*(re: float64; im: float64 = 0.0): Complex64 =
## Returns a `Complex64` with real part `re` and imaginary part `im`.
result.re = re
result.im = im
template im*(arg: typedesc[float32]): Complex32 = complex[float32](0, 1)
template im*(arg: typedesc[float64]): Complex64 = complex[float64](0, 1)
template im*(arg: float32): Complex32 = complex[float32](0, arg)
template im*(arg: float64): Complex64 = complex[float64](0, arg)
template im*(arg: typedesc[float32]): Complex32 = complex32(0, 1)
## Returns the imaginary unit (`complex32(0, 1)`).
template im*(arg: typedesc[float64]): Complex64 = complex64(0, 1)
## Returns the imaginary unit (`complex64(0, 1)`).
template im*(arg: float32): Complex32 = complex32(0, arg)
## Returns `arg` as an imaginary number (`complex32(0, arg)`).
template im*(arg: float64): Complex64 = complex64(0, arg)
## Returns `arg` as an imaginary number (`complex64(0, arg)`).
func abs*[T](z: Complex[T]): T =
## Returns the distance from (0,0) to ``z``.
## Returns the absolute value of `z`,
## that is the distance from (0, 0) to `z`.
result = hypot(z.re, z.im)
func abs2*[T](z: Complex[T]): T =
## Returns the squared distance from (0,0) to ``z``.
result = z.re*z.re + z.im*z.im
## Returns the squared absolute value of `z`,
## that is the squared distance from (0, 0) to `z`.
## This is more efficient than `abs(z) ^ 2`.
result = z.re * z.re + z.im * z.im
func conjugate*[T](z: Complex[T]): Complex[T] =
## Conjugates of complex number ``z``.
## Returns the complex conjugate of `z` (`complex(z.re, -z.im)`).
result.re = z.re
result.im = -z.im
func inv*[T](z: Complex[T]): Complex[T] =
## Multiplicatives inverse of complex number ``z``.
## Returns the multiplicative inverse of `z` (`1/z`).
conjugate(z) / abs2(z)
func `==` *[T](x, y: Complex[T]): bool =
## Compares two complex numbers ``x`` and ``y`` for equality.
func `==`*[T](x, y: Complex[T]): bool =
## Compares two complex numbers for equality.
result = x.re == y.re and x.im == y.im
func `+` *[T](x: T; y: Complex[T]): Complex[T] =
func `+`*[T](x: T; y: Complex[T]): Complex[T] =
## Adds a real number to a complex number.
result.re = x + y.re
result.im = y.im
func `+` *[T](x: Complex[T]; y: T): Complex[T] =
func `+`*[T](x: Complex[T]; y: T): Complex[T] =
## Adds a complex number to a real number.
result.re = x.re + y
result.im = x.im
func `+` *[T](x, y: Complex[T]): Complex[T] =
func `+`*[T](x, y: Complex[T]): Complex[T] =
## Adds two complex numbers.
result.re = x.re + y.re
result.im = x.im + y.im
func `-` *[T](z: Complex[T]): Complex[T] =
func `-`*[T](z: Complex[T]): Complex[T] =
## Unary minus for complex numbers.
result.re = -z.re
result.im = -z.im
func `-` *[T](x: T; y: Complex[T]): Complex[T] =
func `-`*[T](x: T; y: Complex[T]): Complex[T] =
## Subtracts a complex number from a real number.
x + (-y)
result.re = x - y.re
result.im = -y.im
func `-` *[T](x: Complex[T]; y: T): Complex[T] =
func `-`*[T](x: Complex[T]; y: T): Complex[T] =
## Subtracts a real number from a complex number.
result.re = x.re - y
result.im = x.im
func `-` *[T](x, y: Complex[T]): Complex[T] =
func `-`*[T](x, y: Complex[T]): Complex[T] =
## Subtracts two complex numbers.
result.re = x.re - y.re
result.im = x.im - y.im
func `/` *[T](x: Complex[T]; y: T): Complex[T] =
## Divides complex number ``x`` by real number ``y``.
func `*`*[T](x: T; y: Complex[T]): Complex[T] =
## Multiplies a real number with a complex number.
result.re = x * y.re
result.im = x * y.im
func `*`*[T](x: Complex[T]; y: T): Complex[T] =
## Multiplies a complex number with a real number.
result.re = x.re * y
result.im = x.im * y
func `*`*[T](x, y: Complex[T]): Complex[T] =
## Multiplies two complex numbers.
result.re = x.re * y.re - x.im * y.im
result.im = x.im * y.re + x.re * y.im
func `/`*[T](x: Complex[T]; y: T): Complex[T] =
## Divides a complex number by a real number.
result.re = x.re / y
result.im = x.im / y
func `/` *[T](x: T; y: Complex[T]): Complex[T] =
## Divides real number ``x`` by complex number ``y``.
func `/`*[T](x: T; y: Complex[T]): Complex[T] =
## Divides a real number by a complex number.
result = x * inv(y)
func `/` *[T](x, y: Complex[T]): Complex[T] =
## Divides ``x`` by ``y``.
func `/`*[T](x, y: Complex[T]): Complex[T] =
## Divides two complex numbers.
var r, den: T
if abs(y.re) < abs(y.im):
r = y.re / y.im
@@ -119,45 +168,32 @@ func `/` *[T](x, y: Complex[T]): Complex[T] =
result.re = (x.re + r * x.im) / den
result.im = (x.im - r * x.re) / den
func `*` *[T](x: T; y: Complex[T]): Complex[T] =
## Multiplies a real number and a complex number.
result.re = x * y.re
result.im = x * y.im
func `*` *[T](x: Complex[T]; y: T): Complex[T] =
## Multiplies a complex number with a real number.
result.re = x.re * y
result.im = x.im * y
func `*` *[T](x, y: Complex[T]): Complex[T] =
## Multiplies ``x`` with ``y``.
result.re = x.re * y.re - x.im * y.im
result.im = x.im * y.re + x.re * y.im
func `+=` *[T](x: var Complex[T]; y: Complex[T]) =
## Adds ``y`` to ``x``.
func `+=`*[T](x: var Complex[T]; y: Complex[T]) =
## Adds `y` to `x`.
x.re += y.re
x.im += y.im
func `-=` *[T](x: var Complex[T]; y: Complex[T]) =
## Subtracts ``y`` from ``x``.
func `-=`*[T](x: var Complex[T]; y: Complex[T]) =
## Subtracts `y` from `x`.
x.re -= y.re
x.im -= y.im
func `*=` *[T](x: var Complex[T]; y: Complex[T]) =
## Multiplies ``y`` to ``x``.
func `*=`*[T](x: var Complex[T]; y: Complex[T]) =
## Multiplies `x` by `y`.
let im = x.im * y.re + x.re * y.im
x.re = x.re * y.re - x.im * y.im
x.im = im
func `/=` *[T](x: var Complex[T]; y: Complex[T]) =
## Divides ``x`` by ``y`` in place.
func `/=`*[T](x: var Complex[T]; y: Complex[T]) =
## Divides `x` by `y` in place.
x = x / y
func sqrt*[T](z: Complex[T]): Complex[T] =
## Square root for a complex number ``z``.
## Computes the
## ([principal](https://en.wikipedia.org/wiki/Square_root#Principal_square_root_of_a_complex_number))
## square root of a complex number `z`.
var x, y, w, r: T
if z.re == 0.0 and z.im == 0.0:
@@ -180,28 +216,36 @@ func sqrt*[T](z: Complex[T]): Complex[T] =
result.re = z.im / (result.im + result.im)
func exp*[T](z: Complex[T]): Complex[T] =
## ``e`` raised to the power ``z``.
var
## Computes the exponential function (`e^z`).
let
rho = exp(z.re)
theta = z.im
result.re = rho * cos(theta)
result.im = rho * sin(theta)
func ln*[T](z: Complex[T]): Complex[T] =
## Returns the natural log of ``z``.
## Returns the
## ([principal value](https://en.wikipedia.org/wiki/Complex_logarithm#Principal_value)
## of the) natural logarithm of `z`.
result.re = ln(abs(z))
result.im = arctan2(z.im, z.re)
func log10*[T](z: Complex[T]): Complex[T] =
## Returns the log base 10 of ``z``.
## Returns the logarithm base 10 of `z`.
##
## **See also:**
## * `ln func<#ln,Complex[T]>`_
result = ln(z) / ln(10.0)
func log2*[T](z: Complex[T]): Complex[T] =
## Returns the log base 2 of ``z``.
## Returns the logarithm base 2 of `z`.
##
## **See also:**
## * `ln func<#ln,Complex[T]>`_
result = ln(z) / ln(2.0)
func pow*[T](x, y: Complex[T]): Complex[T] =
## ``x`` raised to the power ``y``.
## `x` raised to the power of `y`.
if x.re == 0.0 and x.im == 0.0:
if y.re == 0.0 and y.im == 0.0:
result.re = 1.0
@@ -214,7 +258,7 @@ func pow*[T](x, y: Complex[T]): Complex[T] =
elif y.re == -1.0 and y.im == 0.0:
result = T(1.0) / x
else:
var
let
rho = abs(x)
theta = arctan2(x.im, x.re)
s = pow(rho, y.re) * exp(-y.im * theta)
@@ -223,126 +267,140 @@ func pow*[T](x, y: Complex[T]): Complex[T] =
result.im = s * sin(r)
func pow*[T](x: Complex[T]; y: T): Complex[T] =
## Complex number ``x`` raised to the power ``y``.
## The complex number `x` raised to the power of the real number `y`.
pow(x, complex[T](y))
func sin*[T](z: Complex[T]): Complex[T] =
## Returns the sine of ``z``.
## Returns the sine of `z`.
result.re = sin(z.re) * cosh(z.im)
result.im = cos(z.re) * sinh(z.im)
func arcsin*[T](z: Complex[T]): Complex[T] =
## Returns the inverse sine of ``z``.
## Returns the inverse sine of `z`.
result = -im(T) * ln(im(T) * z + sqrt(T(1.0) - z*z))
func cos*[T](z: Complex[T]): Complex[T] =
## Returns the cosine of ``z``.
## Returns the cosine of `z`.
result.re = cos(z.re) * cosh(z.im)
result.im = -sin(z.re) * sinh(z.im)
func arccos*[T](z: Complex[T]): Complex[T] =
## Returns the inverse cosine of ``z``.
## Returns the inverse cosine of `z`.
result = -im(T) * ln(z + sqrt(z*z - T(1.0)))
func tan*[T](z: Complex[T]): Complex[T] =
## Returns the tangent of ``z``.
## Returns the tangent of `z`.
result = sin(z) / cos(z)
func arctan*[T](z: Complex[T]): Complex[T] =
## Returns the inverse tangent of ``z``.
## Returns the inverse tangent of `z`.
result = T(0.5)*im(T) * (ln(T(1.0) - im(T)*z) - ln(T(1.0) + im(T)*z))
func cot*[T](z: Complex[T]): Complex[T] =
## Returns the cotangent of ``z``.
## Returns the cotangent of `z`.
result = cos(z)/sin(z)
func arccot*[T](z: Complex[T]): Complex[T] =
## Returns the inverse cotangent of ``z``.
## Returns the inverse cotangent of `z`.
result = T(0.5)*im(T) * (ln(T(1.0) - im(T)/z) - ln(T(1.0) + im(T)/z))
func sec*[T](z: Complex[T]): Complex[T] =
## Returns the secant of ``z``.
## Returns the secant of `z`.
result = T(1.0) / cos(z)
func arcsec*[T](z: Complex[T]): Complex[T] =
## Returns the inverse secant of ``z``.
## Returns the inverse secant of `z`.
result = -im(T) * ln(im(T) * sqrt(1.0 - 1.0/(z*z)) + T(1.0)/z)
func csc*[T](z: Complex[T]): Complex[T] =
## Returns the cosecant of ``z``.
## Returns the cosecant of `z`.
result = T(1.0) / sin(z)
func arccsc*[T](z: Complex[T]): Complex[T] =
## Returns the inverse cosecant of ``z``.
## Returns the inverse cosecant of `z`.
result = -im(T) * ln(sqrt(T(1.0) - T(1.0)/(z*z)) + im(T)/z)
func sinh*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic sine of ``z``.
## Returns the hyperbolic sine of `z`.
result = T(0.5) * (exp(z) - exp(-z))
func arcsinh*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic sine of ``z``.
## Returns the inverse hyperbolic sine of `z`.
result = ln(z + sqrt(z*z + 1.0))
func cosh*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic cosine of ``z``.
## Returns the hyperbolic cosine of `z`.
result = T(0.5) * (exp(z) + exp(-z))
func arccosh*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic cosine of ``z``.
## Returns the inverse hyperbolic cosine of `z`.
result = ln(z + sqrt(z*z - T(1.0)))
func tanh*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic tangent of ``z``.
## Returns the hyperbolic tangent of `z`.
result = sinh(z) / cosh(z)
func arctanh*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic tangent of ``z``.
## Returns the inverse hyperbolic tangent of `z`.
result = T(0.5) * (ln((T(1.0)+z) / (T(1.0)-z)))
func sech*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic secant of ``z``.
result = T(2.0) / (exp(z) + exp(-z))
func arcsech*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic secant of ``z``.
result = ln(1.0/z + sqrt(T(1.0)/z+T(1.0)) * sqrt(T(1.0)/z-T(1.0)))
func csch*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic cosecant of ``z``.
result = T(2.0) / (exp(z) - exp(-z))
func arccsch*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic cosecant of ``z``.
result = ln(T(1.0)/z + sqrt(T(1.0)/(z*z) + T(1.0)))
func coth*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic cotangent of ``z``.
## Returns the hyperbolic cotangent of `z`.
result = cosh(z) / sinh(z)
func arccoth*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic cotangent of ``z``.
## Returns the inverse hyperbolic cotangent of `z`.
result = T(0.5) * (ln(T(1.0) + T(1.0)/z) - ln(T(1.0) - T(1.0)/z))
func sech*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic secant of `z`.
result = T(2.0) / (exp(z) + exp(-z))
func arcsech*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic secant of `z`.
result = ln(1.0/z + sqrt(T(1.0)/z+T(1.0)) * sqrt(T(1.0)/z-T(1.0)))
func csch*[T](z: Complex[T]): Complex[T] =
## Returns the hyperbolic cosecant of `z`.
result = T(2.0) / (exp(z) - exp(-z))
func arccsch*[T](z: Complex[T]): Complex[T] =
## Returns the inverse hyperbolic cosecant of `z`.
result = ln(T(1.0)/z + sqrt(T(1.0)/(z*z) + T(1.0)))
func phase*[T](z: Complex[T]): T =
## Returns the phase of ``z``.
## Returns the phase (or argument) of `z`, that is the angle in polar representation.
##
## | `result = arctan2(z.im, z.re)`
arctan2(z.im, z.re)
func polar*[T](z: Complex[T]): tuple[r, phi: T] =
## Returns ``z`` in polar coordinates.
## Returns `z` in polar coordinates.
##
## | `result.r = abs(z)`
## | `result.phi = phase(z)`
##
## **See also:**
## * `rect func<#rect,T,T>`_ for the inverse operation
(r: abs(z), phi: phase(z))
func rect*[T](r, phi: T): Complex[T] =
## Returns the complex number with polar coordinates ``r`` and ``phi``.
## Returns the complex number with polar coordinates `r` and `phi`.
##
## | ``result.re = r * cos(phi)``
## | ``result.im = r * sin(phi)``
## | `result.re = r * cos(phi)`
## | `result.im = r * sin(phi)`
##
## **See also:**
## * `polar func<#polar,Complex[T]>`_ for the inverse operation
complex(r * cos(phi), r * sin(phi))
func `$`*(z: Complex): string =
## Returns ``z``'s string representation as ``"(re, im)"``.
## Returns `z`'s string representation as `"(re, im)"`.
runnableExamples:
doAssert $complex(1.0, 2.0) == "(1.0, 2.0)"
result = "(" & $z.re & ", " & $z.im & ")"
{.pop.}

View File

@@ -1,4 +1,4 @@
import complex, math
import std/[complex, math]
proc `=~`[T](x, y: Complex[T]): bool =
@@ -7,7 +7,7 @@ proc `=~`[T](x, y: Complex[T]): bool =
proc `=~`[T](x: Complex[T]; y: T): bool =
result = abs(x.re-y) < 1e-6 and abs(x.im) < 1e-6
var
let
z: Complex64 = complex(0.0, 0.0)
oo: Complex64 = complex(1.0, 1.0)
a: Complex64 = complex(1.0, 2.0)
@@ -76,12 +76,12 @@ doAssert(arccsch(a) =~ arcsinh(1.0/a))
doAssert(arccoth(a) =~ arctanh(1.0/a))
doAssert(phase(a) == 1.1071487177940904)
var t = polar(a)
let t = polar(a)
doAssert(rect(t.r, t.phi) =~ a)
doAssert(rect(1.0, 2.0) =~ complex(-0.4161468365471424, 0.9092974268256817))
var
let
i64: Complex32 = complex(0.0f, 1.0f)
a64: Complex32 = 2.0f*i64 + 1.0.float32
b64: Complex32 = complex(-1.0'f32, -2.0'f32)
@@ -96,7 +96,7 @@ doAssert(sin(arcsin(b64)) =~ b64)
doAssert(cosh(arccosh(a64)) =~ a64)
doAssert(phase(a64) - 1.107149f < 1e-6)
var t64 = polar(a64)
let t64 = polar(a64)
doAssert(rect(t64.r, t64.phi) =~ a64)
doAssert(rect(1.0f, 2.0f) =~ complex(-0.4161468f, 0.90929742f))
doAssert(sizeof(a64) == 8)
@@ -104,5 +104,5 @@ doAssert(sizeof(a) == 16)
doAssert 123.0.im + 456.0 == complex64(456, 123)
var localA = complex(0.1'f32)
let localA = complex(0.1'f32)
doAssert localA.im is float32