feat: sin and cos non-finite (#17)

Author: polvalente

lib/complex.ex

@@ -973,14 +973,19 @@ defmodule Complex do
   def sin(n) when is_number(n), do: :math.sin(n)
   def sin(n) when is_non_finite_number(n), do: :nan
 
-  def sin(%Complex{re: re, im: _}) when is_non_finite_number(re), do: :nan
+  def sin(%Complex{re: re, im: im}) when is_non_finite_number(re) and is_number(im),
+    do: Complex.new(:nan, :nan)
 
-  def sin(%Complex{re: re, im: im}) when is_number(re) and is_non_finite_number(im),
-    do:
-      new(
-        multiply(:math.sin(re), cosh(im)),
-        multiply(:math.sin(re), sinh(im))
-      )
+  def sin(%Complex{im: :nan}), do: Complex.new(:nan, :nan)
+  def sin(%Complex{re: :nan}), do: Complex.new(:nan, :nan)
+
+  def sin(%Complex{re: re, im: im}) when is_number(re) and is_non_finite_number(im) do
+    Complex.new(multiply(re, im), im)
+  end
+
+  def sin(%Complex{re: re, im: im}) when is_non_finite_number(re) and is_non_finite_number(im) do
+    Complex.new(:nan, :nan)
+  end
 
   def sin(z = %Complex{}) do
     new(
@@ -1065,11 +1070,18 @@ defmodule Complex do
 
   def cos(n) when is_non_finite_number(n), do: :nan
 
+  def cos(%Complex{re: re, im: im}) when is_non_finite_number(re) and is_number(im),
+    do: Complex.new(:nan, :nan)
+
+  def cos(%Complex{im: :nan}), do: Complex.new(:nan, :nan)
+  def cos(%Complex{re: :nan}), do: Complex.new(:nan, :nan)
+
   def cos(%Complex{re: re, im: im}) when is_number(re) and is_non_finite_number(im) do
-    new(
-      multiply(:math.cos(re), cosh(im)),
-      multiply(:math.sin(-re), sinh(im))
-    )
+    Complex.new(:infinity, -1 |> multiply(im) |> multiply(re))
+  end
+
+  def cos(%Complex{re: re, im: im}) when is_non_finite_number(re) and is_non_finite_number(im) do
+    Complex.new(:nan, :nan)
   end
 
   def cos(z = %Complex{}) do

test/complex_test.exs

@@ -602,6 +602,34 @@ defmodule ComplexTest do
     assert_close Complex.acsc(7.086167), :math.pi() - a
   end
 
+  test "sin (non-finite)" do
+    assert Complex.sin(Complex.new(:nan)) == Complex.new(:nan, :nan)
+    assert Complex.sin(Complex.new(:infinity)) == Complex.new(:nan, :nan)
+    assert Complex.sin(Complex.new(:neg_infinity)) == Complex.new(:nan, :nan)
+    assert Complex.sin(Complex.new(0, :nan)) == Complex.new(:nan, :nan)
+    assert Complex.sin(Complex.new(0, :infinity)) == Complex.new(:nan, :infinity)
+    assert Complex.sin(Complex.new(0, :neg_infinity)) == Complex.new(:nan, :neg_infinity)
+
+    assert Complex.sin(Complex.new(-1, :infinity)) == Complex.new(:neg_infinity, :infinity)
+    assert Complex.sin(Complex.new(1, :infinity)) == Complex.new(:infinity, :infinity)
+    assert Complex.sin(Complex.new(-1, :neg_infinity)) == Complex.new(:infinity, :neg_infinity)
+    assert Complex.sin(Complex.new(1, :neg_infinity)) == Complex.new(:neg_infinity, :neg_infinity)
+  end
+
+  test "cos (non-finite)" do
+    assert Complex.cos(Complex.new(:nan)) == Complex.new(:nan, :nan)
+    assert Complex.cos(Complex.new(:infinity)) == Complex.new(:nan, :nan)
+    assert Complex.cos(Complex.new(:neg_infinity)) == Complex.new(:nan, :nan)
+    assert Complex.cos(Complex.new(0, :nan)) == Complex.new(:nan, :nan)
+    assert Complex.cos(Complex.new(0, :infinity)) == Complex.new(:infinity, :nan)
+    assert Complex.cos(Complex.new(0, :neg_infinity)) == Complex.new(:infinity, :nan)
+
+    assert Complex.cos(Complex.new(-1, :infinity)) == Complex.new(:infinity, :infinity)
+    assert Complex.cos(Complex.new(1, :infinity)) == Complex.new(:infinity, :neg_infinity)
+    assert Complex.cos(Complex.new(-1, :neg_infinity)) == Complex.new(:infinity, :neg_infinity)
+    assert Complex.cos(Complex.new(1, :neg_infinity)) == Complex.new(:infinity, :infinity)
+  end
+
   test "Hyperbolic functions" do
     a = Complex.new(1.0, 2.0)
     assert_close Complex.sinh(a), %Complex{re: -0.48905625904129363, im: 1.4031192506220405}