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diff --git a/lib/pure/complex.nim b/lib/pure/complex.nim
index d57adeb92..b48811eae 100644
--- a/lib/pure/complex.nim
+++ b/lib/pure/complex.nim
@@ -7,157 +7,186 @@
 #    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
+
+  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, strformat]
 
 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.
 
-proc complex*[T: SomeFloat](re: T; im: T = 0.0): Complex[T] =
+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
 
-proc 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
 
-proc 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)
-
-proc abs*[T](z: Complex[T]): T =
-  ## Return the distance from (0,0) to ``z``.
+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 absolute value of `z`,
+  ## that is the distance from (0, 0) to `z`.
   result = hypot(z.re, z.im)
 
-proc abs2*[T](z: Complex[T]): T =
-  ## Return the squared distance from (0,0) to ``z``.
-  result = z.re*z.re + z.im*z.im
-
-proc conjugate*[T](z: Complex[T]): Complex[T] =
-  ## Conjugate of complex number ``z``.
+func abs2*[T](z: Complex[T]): T =
+  ## 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 sgn*[T](z: Complex[T]): Complex[T] =
+  ## Returns the phase of `z` as a unit complex number,
+  ## or 0 if `z` is 0.
+  let a = abs(z)
+  if a != 0:
+    result = z / a
+
+func conjugate*[T](z: Complex[T]): Complex[T] =
+  ## Returns the complex conjugate of `z` (`complex(z.re, -z.im)`).
   result.re = z.re
   result.im = -z.im
 
-proc inv*[T](z: Complex[T]): Complex[T] =
-  ## Multiplicative inverse of complex number ``z``.
+func inv*[T](z: Complex[T]): Complex[T] =
+  ## Returns the multiplicative inverse of `z` (`1/z`).
   conjugate(z) / abs2(z)
 
-proc `==` *[T](x, y: Complex[T]): bool =
-  ## Compare 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
 
-proc `+` *[T](x: T; y: Complex[T]): Complex[T] =
-  ## Add a real number to a complex number.
+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
 
-proc `+` *[T](x: Complex[T]; y: T): Complex[T] =
-  ## Add a complex number to a real number.
+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
 
-proc `+` *[T](x, y: Complex[T]): Complex[T] =
-  ## Add two complex numbers.
+func `+`*[T](x, y: Complex[T]): Complex[T] =
+  ## Adds two complex numbers.
   result.re = x.re + y.re
   result.im = x.im + y.im
 
-proc `-` *[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
 
-proc `-` *[T](x: T; y: Complex[T]): Complex[T] =
-  ## Subtract a complex number from a real number.
-  x + (-y)
+func `-`*[T](x: T; y: Complex[T]): Complex[T] =
+  ## Subtracts a complex number from a real number.
+  result.re = x - y.re
+  result.im = -y.im
 
-proc `-` *[T](x: Complex[T]; y: T): Complex[T] =
-  ## Subtract a real number from a complex number.
+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
 
-proc `-` *[T](x, y: Complex[T]): Complex[T] =
-  ## Subtract two complex numbers.
+func `-`*[T](x, y: Complex[T]): Complex[T] =
+  ## Subtracts two complex numbers.
   result.re = x.re - y.re
   result.im = x.im - y.im
 
-proc `/` *[T](x: Complex[T]; y: T): Complex[T] =
-  ## Divide complex number ``x`` by real number ``y``.
-  result.re = x.re / y
-  result.im = x.im / y
-
-proc `/` *[T](x: T; y: Complex[T]): Complex[T] =
-  ## Divide real number ``x`` by complex number ``y``.
-  result = x * inv(y)
-
-proc `/` *[T](x, y: Complex[T]): Complex[T] =
-  ## Divide ``x`` by ``y``.
-  var r, den: T
-  if abs(y.re) < abs(y.im):
-    r = y.re / y.im
-    den = y.im + r * y.re
-    result.re = (x.re * r + x.im) / den
-    result.im = (x.im * r - x.re) / den
-  else:
-    r = y.im / y.re
-    den = y.re + r * y.im
-    result.re = (x.re + r * x.im) / den
-    result.im = (x.im - r * x.re) / den
-
-proc `*` *[T](x: T; y: Complex[T]): Complex[T] =
-  ## Multiply a real number and a complex number.
+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
 
-proc `*` *[T](x: Complex[T]; y: T): Complex[T] =
-  ## Multiply a complex number with a real number.
+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
 
-proc `*` *[T](x, y: Complex[T]): Complex[T] =
-  ## Multiply ``x`` with ``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
 
-proc `+=` *[T](x: var Complex[T]; y: Complex[T]) =
-  ## Add ``y`` to ``x``.
+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 two complex numbers.
+  x * conjugate(y) / abs2(y)
+
+func `+=`*[T](x: var Complex[T]; y: Complex[T]) =
+  ## Adds `y` to `x`.
   x.re += y.re
   x.im += y.im
 
-proc `-=` *[T](x: var Complex[T]; y: Complex[T]) =
-  ## Subtract ``y`` from ``x``.
+func `-=`*[T](x: var Complex[T]; y: Complex[T]) =
+  ## Subtracts `y` from `x`.
   x.re -= y.re
   x.im -= y.im
 
-proc `*=` *[T](x: var Complex[T]; y: Complex[T]) =
-  ## Multiply ``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
 
-proc `/=` *[T](x: var Complex[T]; y: Complex[T]) =
-  ## Divide ``x`` by ``y`` in place.
+func `/=`*[T](x: var Complex[T]; y: Complex[T]) =
+  ## Divides `x` by `y` in place.
   x = x / y
 
 
-proc sqrt*[T](z: Complex[T]): Complex[T] =
-  ## Square root for a complex number ``z``.
+func sqrt*[T](z: Complex[T]): Complex[T] =
+  ## 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:
@@ -179,29 +208,37 @@ proc sqrt*[T](z: Complex[T]): Complex[T] =
       result.im = if z.im >= 0.0: w else: -w
       result.re = z.im / (result.im + result.im)
 
-proc exp*[T](z: Complex[T]): Complex[T] =
-  ## ``e`` raised to the power ``z``.
-  var
+func exp*[T](z: Complex[T]): Complex[T] =
+  ## Computes the exponential function (`e^z`).
+  let
     rho = exp(z.re)
     theta = z.im
   result.re = rho * cos(theta)
   result.im = rho * sin(theta)
 
-proc ln*[T](z: Complex[T]): Complex[T] =
-  ## Returns the natural log of ``z``.
+func ln*[T](z: Complex[T]): Complex[T] =
+  ## 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)
 
-proc log10*[T](z: Complex[T]): Complex[T] =
-  ## Returns the log base 10 of ``z``.
+func log10*[T](z: Complex[T]): Complex[T] =
+  ## Returns the logarithm base 10 of `z`.
+  ##
+  ## **See also:**
+  ## * `ln func<#ln,Complex[T]>`_
   result = ln(z) / ln(10.0)
 
-proc log2*[T](z: Complex[T]): Complex[T] =
-  ## Returns the log base 2 of ``z``.
+func log2*[T](z: Complex[T]): Complex[T] =
+  ## Returns the logarithm base 2 of `z`.
+  ##
+  ## **See also:**
+  ## * `ln func<#ln,Complex[T]>`_
   result = ln(z) / ln(2.0)
 
-proc pow*[T](x, y: Complex[T]): Complex[T] =
-  ## ``x`` raised to the power ``y``.
+func pow*[T](x, y: Complex[T]): Complex[T] =
+  ## `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
@@ -209,12 +246,33 @@ proc pow*[T](x, y: Complex[T]): Complex[T] =
     else:
       result.re = 0.0
       result.im = 0.0
-  elif y.re == 1.0 and y.im == 0.0:
-    result = x
-  elif y.re == -1.0 and y.im == 0.0:
-    result = T(1.0) / x
+  elif y.im == 0.0:
+    if y.re == 1.0:
+      result = x
+    elif y.re == -1.0:
+      result = T(1.0) / x
+    elif y.re == 2.0:
+      result = x * x
+    elif y.re == 0.5:
+      result = sqrt(x)
+    elif x.im == 0.0:
+      # Revert to real pow when both base and exponent are real
+      result.re = pow(x.re, y.re)
+      result.im = 0.0
+    else:
+      # Special case when the exponent is real
+      let
+        rho = abs(x)
+        theta = arctan2(x.im, x.re)
+        s = pow(rho, y.re)
+        r = y.re * theta
+      result.re = s * cos(r)
+      result.im = s * sin(r)
+  elif x.im == 0.0 and x.re == E:
+   # Special case Euler's formula
+   result = exp(y)
   else:
-    var
+    let
       rho = abs(x)
       theta = arctan2(x.im, x.re)
       s = pow(rho, y.re) * exp(-y.im * theta)
@@ -222,235 +280,194 @@ proc pow*[T](x, y: Complex[T]): Complex[T] =
     result.re = s * cos(r)
     result.im = s * sin(r)
 
-proc pow*[T](x: Complex[T]; y: T): Complex[T] =
-  ## Complex number ``x`` raised to the power ``y``.
+func pow*[T](x: Complex[T]; y: T): Complex[T] =
+  ## The complex number `x` raised to the power of the real number `y`.
   pow(x, complex[T](y))
 
 
-proc sin*[T](z: Complex[T]): Complex[T] =
-  ## Returns the sine of ``z``.
+func sin*[T](z: Complex[T]): Complex[T] =
+  ## Returns the sine of `z`.
   result.re = sin(z.re) * cosh(z.im)
   result.im = cos(z.re) * sinh(z.im)
 
-proc arcsin*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse sine of ``z``.
+func arcsin*[T](z: Complex[T]): Complex[T] =
+  ## Returns the inverse sine of `z`.
   result = -im(T) * ln(im(T) * z + sqrt(T(1.0) - z*z))
 
-proc cos*[T](z: Complex[T]): Complex[T] =
-  ## Returns the cosine of ``z``.
+func cos*[T](z: Complex[T]): Complex[T] =
+  ## Returns the cosine of `z`.
   result.re = cos(z.re) * cosh(z.im)
   result.im = -sin(z.re) * sinh(z.im)
 
-proc arccos*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse cosine of ``z``.
+func arccos*[T](z: Complex[T]): Complex[T] =
+  ## Returns the inverse cosine of `z`.
   result = -im(T) * ln(z + sqrt(z*z - T(1.0)))
 
-proc tan*[T](z: Complex[T]): Complex[T] =
-  ## Returns the tangent of ``z``.
+func tan*[T](z: Complex[T]): Complex[T] =
+  ## Returns the tangent of `z`.
   result = sin(z) / cos(z)
 
-proc arctan*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse tangent of ``z``.
+func arctan*[T](z: Complex[T]): Complex[T] =
+  ## 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))
 
-proc cot*[T](z: Complex[T]): Complex[T] =
-  ## Returns the cotangent of ``z``.
+func cot*[T](z: Complex[T]): Complex[T] =
+  ## Returns the cotangent of `z`.
   result = cos(z)/sin(z)
 
-proc arccot*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse cotangent of ``z``.
+func arccot*[T](z: Complex[T]): Complex[T] =
+  ## 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))
 
-proc sec*[T](z: Complex[T]): Complex[T] =
-  ## Returns the secant of ``z``.
+func sec*[T](z: Complex[T]): Complex[T] =
+  ## Returns the secant of `z`.
   result = T(1.0) / cos(z)
 
-proc arcsec*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse secant of ``z``.
+func arcsec*[T](z: Complex[T]): Complex[T] =
+  ## Returns the inverse secant of `z`.
   result = -im(T) * ln(im(T) * sqrt(1.0 - 1.0/(z*z)) + T(1.0)/z)
 
-proc csc*[T](z: Complex[T]): Complex[T] =
-  ## Returns the cosecant of ``z``.
+func csc*[T](z: Complex[T]): Complex[T] =
+  ## Returns the cosecant of `z`.
   result = T(1.0) / sin(z)
 
-proc arccsc*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse cosecant of ``z``.
+func arccsc*[T](z: Complex[T]): Complex[T] =
+  ## Returns the inverse cosecant of `z`.
   result = -im(T) * ln(sqrt(T(1.0) - T(1.0)/(z*z)) + im(T)/z)
 
-proc sinh*[T](z: Complex[T]): Complex[T] =
-  ## Returns the hyperbolic sine of ``z``.
+func sinh*[T](z: Complex[T]): Complex[T] =
+  ## Returns the hyperbolic sine of `z`.
   result = T(0.5) * (exp(z) - exp(-z))
 
-proc arcsinh*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse hyperbolic sine of ``z``.
+func arcsinh*[T](z: Complex[T]): Complex[T] =
+  ## Returns the inverse hyperbolic sine of `z`.
   result = ln(z + sqrt(z*z + 1.0))
 
-proc cosh*[T](z: Complex[T]): Complex[T] =
-  ## Returns the hyperbolic cosine of ``z``.
+func cosh*[T](z: Complex[T]): Complex[T] =
+  ## Returns the hyperbolic cosine of `z`.
   result = T(0.5) * (exp(z) + exp(-z))
 
-proc arccosh*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse hyperbolic cosine of ``z``.
+func arccosh*[T](z: Complex[T]): Complex[T] =
+  ## Returns the inverse hyperbolic cosine of `z`.
   result = ln(z + sqrt(z*z - T(1.0)))
 
-proc tanh*[T](z: Complex[T]): Complex[T] =
-  ## Returns the hyperbolic tangent of ``z``.
+func tanh*[T](z: Complex[T]): Complex[T] =
+  ## Returns the hyperbolic tangent of `z`.
   result = sinh(z) / cosh(z)
 
-proc arctanh*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse hyperbolic tangent of ``z``.
+func arctanh*[T](z: Complex[T]): Complex[T] =
+  ## Returns the inverse hyperbolic tangent of `z`.
   result = T(0.5) * (ln((T(1.0)+z) / (T(1.0)-z)))
 
-proc sech*[T](z: Complex[T]): Complex[T] =
-  ## Returns the hyperbolic secant of ``z``.
+func coth*[T](z: Complex[T]): Complex[T] =
+  ## 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`.
+  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))
 
-proc arcsech*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse hyperbolic secant of ``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)))
 
-proc csch*[T](z: Complex[T]): Complex[T] =
-  ## Returns the hyperbolic cosecant of ``z``.
+func csch*[T](z: Complex[T]): Complex[T] =
+  ## Returns the hyperbolic cosecant of `z`.
   result = T(2.0) / (exp(z) - exp(-z))
 
-proc arccsch*[T](z: Complex[T]): Complex[T] =
-  ## Returns the inverse hyperbolic cosecant of ``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)))
 
-proc coth*[T](z: Complex[T]): Complex[T] =
-  ## Returns the hyperbolic cotangent of ``z``.
-  result = cosh(z) / sinh(z)
-
-proc arccoth*[T](z: Complex[T]): Complex[T] =
-  ## 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))
-
-proc phase*[T](z: Complex[T]): T =
-  ## Returns the phase of ``z``.
+func phase*[T](z: Complex[T]): T =
+  ## 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)
 
-proc polar*[T](z: Complex[T]): tuple[r, phi: T] =
-  ## Returns ``z`` in polar coordinates.
+func polar*[T](z: Complex[T]): tuple[r, phi: T] =
+  ## 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))
 
-proc rect*[T](r, phi: T): Complex[T] =
-  ## Returns the complex number with polar coordinates ``r`` and ``phi``.
+func rect*[T](r, phi: T): Complex[T] =
+  ## 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 almostEqual*[T: SomeFloat](x, y: Complex[T]; unitsInLastPlace: Natural = 4): bool =
+  ## Checks if two complex values are almost equal, using the
+  ## [machine epsilon](https://en.wikipedia.org/wiki/Machine_epsilon).
+  ##
+  ## Two complex values are considered almost equal if their real and imaginary
+  ## components are almost equal.
+  ##
+  ## `unitsInLastPlace` is the max number of
+  ## [units in the last place](https://en.wikipedia.org/wiki/Unit_in_the_last_place)
+  ## difference tolerated when comparing two numbers. The larger the value, the
+  ## more error is allowed. A `0` value means that two numbers must be exactly the
+  ## same to be considered equal.
+  ##
+  ## The machine epsilon has to be scaled to the magnitude of the values used
+  ## and multiplied by the desired precision in ULPs unless the difference is
+  ## subnormal.
+  almostEqual(x.re, y.re, unitsInLastPlace = unitsInLastPlace) and
+  almostEqual(x.im, y.im, unitsInLastPlace = unitsInLastPlace)
 
-proc `$`*(z: Complex): string =
-  ## Returns ``z``'s string representation as ``"(re, im)"``.
-  result = "(" & $z.re & ", " & $z.im & ")"
+func `$`*(z: Complex): string =
+  ## Returns `z`'s string representation as `"(re, im)"`.
+  runnableExamples:
+    doAssert $complex(1.0, 2.0) == "(1.0, 2.0)"
 
-{.pop.}
+  result = "(" & $z.re & ", " & $z.im & ")"
 
+proc formatValueAsTuple(result: var string; value: Complex; specifier: string) =
+  ## Format implementation for `Complex` representing the value as a (real, imaginary) tuple.
+  result.add "("
+  formatValue(result, value.re, specifier)
+  result.add ", "
+  formatValue(result, value.im, specifier)
+  result.add ")"
+
+proc formatValueAsComplexNumber(result: var string; value: Complex; specifier: string) =
+  ## Format implementation for `Complex` representing the value as a (RE+IMj) number
+  ## By default, the real and imaginary parts are formatted using the general ('g') format
+  let specifier = if specifier.contains({'e', 'E', 'f', 'F', 'g', 'G'}):
+      specifier.replace("j")
+    else:
+      specifier.replace('j', 'g')
+  result.add "("
+  formatValue(result, value.re, specifier)
+  if value.im >= 0 and not specifier.contains({'+', '-'}):
+    result.add "+"
+  formatValue(result, value.im, specifier)
+  result.add "j)"
+
+proc formatValue*(result: var string; value: Complex; specifier: string) =
+  ## Standard format implementation for `Complex`. It makes little
+  ## sense to call this directly, but it is required to exist
+  ## by the `&` macro.
+  ## For complex numbers, we add a specific 'j' specifier, which formats
+  ## the value as (A+Bj) like in mathematics.
+  if specifier.len == 0:
+    result.add $value
+  elif 'j' in specifier:
+    formatValueAsComplexNumber(result, value, specifier)
+  else:
+    formatValueAsTuple(result, value, specifier)
 
-when isMainModule:
-  proc `=~`[T](x, y: Complex[T]): bool =
-    result = abs(x.re-y.re) < 1e-6 and abs(x.im-y.im) < 1e-6
-
-  proc `=~`[T](x: Complex[T]; y: T): bool =
-    result = abs(x.re-y) < 1e-6 and abs(x.im) < 1e-6
-
-  var
-    z: Complex64 = complex(0.0, 0.0)
-    oo: Complex64 = complex(1.0, 1.0)
-    a: Complex64 = complex(1.0, 2.0)
-    b: Complex64 = complex(-1.0, -2.0)
-    m1: Complex64 = complex(-1.0, 0.0)
-    i: Complex64 = complex(0.0, 1.0)
-    one: Complex64 = complex(1.0, 0.0)
-    tt: Complex64 = complex(10.0, 20.0)
-    ipi: Complex64 = complex(0.0, -PI)
-
-  doAssert(a/2.0 =~ complex(0.5, 1.0))
-  doAssert(a == a)
-  doAssert((a-a) == z)
-  doAssert((a+b) == z)
-  doAssert((a+b) =~ 0.0)
-  doAssert((a/b) == m1)
-  doAssert((1.0/a) =~ complex(0.2, -0.4))
-  doAssert((a*b) == complex(3.0, -4.0))
-  doAssert(10.0*a == tt)
-  doAssert(a*10.0 == tt)
-  doAssert(tt/10.0 == a)
-  doAssert(oo+(-1.0) == i)
-  doAssert( (-1.0)+oo == i)
-  doAssert(abs(oo) == sqrt(2.0))
-  doAssert(conjugate(a) == complex(1.0, -2.0))
-  doAssert(sqrt(m1) == i)
-  doAssert(exp(ipi) =~ m1)
-
-  doAssert(pow(a, b) =~ complex(-3.72999124927876, -1.68815826725068))
-  doAssert(pow(z, a) =~ complex(0.0, 0.0))
-  doAssert(pow(z, z) =~ complex(1.0, 0.0))
-  doAssert(pow(a, one) =~ a)
-  doAssert(pow(a, m1) =~ complex(0.2, -0.4))
-  doAssert(pow(a, 2.0) =~ complex(-3.0, 4.0))
-  doAssert(pow(a, 2) =~ complex(-3.0, 4.0))
-  doAssert(not(pow(a, 2.0) =~ a))
-
-  doAssert(ln(a) =~ complex(0.804718956217050, 1.107148717794090))
-  doAssert(log10(a) =~ complex(0.349485002168009, 0.480828578784234))
-  doAssert(log2(a) =~ complex(1.16096404744368, 1.59727796468811))
-
-  doAssert(sin(a) =~ complex(3.16577851321617, 1.95960104142161))
-  doAssert(cos(a) =~ complex(2.03272300701967, -3.05189779915180))
-  doAssert(tan(a) =~ complex(0.0338128260798967, 1.0147936161466335))
-  doAssert(cot(a) =~ 1.0 / tan(a))
-  doAssert(sec(a) =~ 1.0 / cos(a))
-  doAssert(csc(a) =~ 1.0 / sin(a))
-  doAssert(arcsin(a) =~ complex(0.427078586392476, 1.528570919480998))
-  doAssert(arccos(a) =~ complex(1.14371774040242, -1.52857091948100))
-  doAssert(arctan(a) =~ complex(1.338972522294494, 0.402359478108525))
-  doAssert(arccot(a) =~ complex(0.2318238045004031, -0.402359478108525))
-  doAssert(arcsec(a) =~ complex(1.384478272687081, 0.3965682301123288))
-  doAssert(arccsc(a) =~ complex(0.1863180541078155, -0.3965682301123291))
-
-  doAssert(cosh(a) =~ complex(-0.642148124715520, 1.068607421382778))
-  doAssert(sinh(a) =~ complex(-0.489056259041294, 1.403119250622040))
-  doAssert(tanh(a) =~ complex(1.1667362572409199, -0.243458201185725))
-  doAssert(sech(a) =~ 1.0 / cosh(a))
-  doAssert(csch(a) =~ 1.0 / sinh(a))
-  doAssert(coth(a) =~ 1.0 / tanh(a))
-  doAssert(arccosh(a) =~ complex(1.528570919480998, 1.14371774040242))
-  doAssert(arcsinh(a) =~ complex(1.469351744368185, 1.06344002357775))
-  doAssert(arctanh(a) =~ complex(0.173286795139986, 1.17809724509617))
-  doAssert(arcsech(a) =~ arccosh(1.0/a))
-  doAssert(arccsch(a) =~ arcsinh(1.0/a))
-  doAssert(arccoth(a) =~ arctanh(1.0/a))
-
-  doAssert(phase(a) == 1.1071487177940904)
-  var t = polar(a)
-  doAssert(rect(t.r, t.phi) =~ a)
-  doAssert(rect(1.0, 2.0) =~ complex(-0.4161468365471424, 0.9092974268256817))
-
-
-  var
-    i64: Complex32 = complex(0.0f, 1.0f)
-    a64: Complex32 = 2.0f*i64 + 1.0.float32
-    b64: Complex32 = complex(-1.0'f32, -2.0'f32)
-
-  doAssert(a64 == a64)
-  doAssert(a64 == -b64)
-  doAssert(a64 + b64 =~ 0.0'f32)
-  doAssert(not(pow(a64, b64) =~ a64))
-  doAssert(pow(a64, 0.5f) =~ sqrt(a64))
-  doAssert(pow(a64, 2) =~ complex(-3.0'f32, 4.0'f32))
-  doAssert(sin(arcsin(b64)) =~ b64)
-  doAssert(cosh(arccosh(a64)) =~ a64)
-
-  doAssert(phase(a64) - 1.107149f < 1e-6)
-  var 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)
-  doAssert(sizeof(a) == 16)
-
-  doAssert 123.0.im + 456.0 == complex64(456, 123)
-
-  var localA = complex(0.1'f32)
-  doAssert localA.im is float32
+{.pop.}