Drop BigDecimal

`BigDecimal` was introduced early in the project from my belief that high accuracy was needed. It turns out that the number of digits in floats are enough to keep a precision up to 0.0001 arcseconds in most calculations. Using `BigDecimal` has a cost over the overall performance of the library. If it is not absolutely necessary for the calculations, it's better not to use it.
rhannequin · Apr 2, 2024 · 26fb8b4 · 26fb8b4
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diff --git a/README.md b/README.md
@@ -32,7 +32,7 @@ major one is released.
 
 ```rb
 angle1 = Astronoby::Angle.from_degrees(90)
-angle2 = Astronoby::Angle.from_radians(Astronoby::Angle::PI / 2)
+angle2 = Astronoby::Angle.from_radians(Math::PI / 2)
 angle3 = Astronoby::Angle.from_hours(12)
 
 angle1 == angle2
@@ -83,8 +83,8 @@ horizontal_coordinates = sun.horizontal_coordinates(
   longitude: longitude
 )
 
-horizontal_coordinates.altitude.degrees.to_f
-# => 27.50008242057459
+horizontal_coordinates.altitude.degrees
+# => 27.500082420575094
 
 horizontal_coordinates.altitude.str(:dms)
 # => "+27° 30′ 0.2967″"

diff --git a/lib/astronoby/angle.rb b/lib/astronoby/angle.rb
@@ -1,21 +1,18 @@
 # frozen_string_literal: true
 
-require "bigdecimal/math"
-
 module Astronoby
   class Angle
     include Comparable
 
-    PRECISION = 14
-    PI = BigMath.PI(PRECISION)
-    PI_IN_DEGREES = BigDecimal("180")
+    MIN_PRECISION = 10
+    PI_IN_DEGREES = 180.0
 
-    FULL_CIRCLE_IN_RADIANS = (2 * PI)
+    FULL_CIRCLE_IN_RADIANS = (2 * Math::PI)
 
-    RADIAN_PER_HOUR = PI / BigDecimal("12")
-    MINUTES_PER_DEGREE = BigDecimal("60")
-    MINUTES_PER_HOUR = BigDecimal("60")
-    SECONDS_PER_MINUTE = BigDecimal("60")
+    RADIAN_PER_HOUR = Math::PI / 12.0
+    MINUTES_PER_DEGREE = 60.0
+    MINUTES_PER_HOUR = 60.0
+    SECONDS_PER_MINUTE = 60.0
     SECONDS_PER_HOUR = MINUTES_PER_HOUR * SECONDS_PER_MINUTE
 
     FORMATS = %i[dms hms].freeze
@@ -31,7 +28,7 @@ def from_radians(radians)
       end
 
       def from_degrees(degrees)
-        radians = degrees / PI_IN_DEGREES * PI
+        radians = degrees / PI_IN_DEGREES * Math::PI
         from_radians(radians)
       end
 
@@ -70,16 +67,12 @@ def atan(ratio)
     attr_reader :radians
 
     def initialize(radians)
-      @radians = if radians.is_a?(Integer) || radians.is_a?(BigDecimal)
-        BigDecimal(radians)
-      else
-        BigDecimal(radians, PRECISION)
-      end
+      @radians = radians
       freeze
     end
 
     def degrees
-      @radians * PI_IN_DEGREES / PI
+      @radians * PI_IN_DEGREES / Math::PI
     end
 
     def hours
@@ -153,7 +146,7 @@ def to_dms(deg)
         absolute_decimal_minutes - absolute_decimal_minutes.floor
       )
 
-      Dms.new(sign, degrees, minutes, seconds.to_f.floor(4))
+      Dms.new(sign, degrees, minutes, seconds.floor(4))
     end
 
     def to_hms(hrs)
@@ -168,7 +161,7 @@ def to_hms(hrs)
         absolute_decimal_minutes - absolute_decimal_minutes.floor
       )
 
-      Hms.new(hours, minutes, seconds.to_f.floor(4))
+      Hms.new(hours, minutes, seconds.floor(4))
     end
   end
 end
diff --git a/lib/astronoby/bodies/sun.rb b/lib/astronoby/bodies/sun.rb
@@ -4,7 +4,7 @@ module Astronoby
   class Sun
     SEMI_MAJOR_AXIS_IN_METERS = 149_598_500_000
     ANGULAR_DIAMETER = Angle.from_degrees(0.533128)
-    INTERPOLATION_FACTOR = BigDecimal("24.07")
+    INTERPOLATION_FACTOR = 24.07
 
     # Source:
     #  Title: Practical Astronomy with your Calculator or Spreadsheet

diff --git a/lib/astronoby/coordinates/equatorial.rb b/lib/astronoby/coordinates/equatorial.rb
@@ -39,7 +39,7 @@ def to_horizontal(time:, latitude:, longitude:)
         azimuth = Angle.acos(t2)
 
         if ha.sin.positive?
-          azimuth = Angle.from_degrees(BigDecimal("360") - azimuth.degrees)
+          azimuth = Angle.from_degrees(360 - azimuth.degrees)
         end
 
         Horizontal.new(

diff --git a/lib/astronoby/coordinates/horizontal.rb b/lib/astronoby/coordinates/horizontal.rb
@@ -31,7 +31,7 @@ def to_equatorial(time:)
 
         if @azimuth.sin.positive?
           hour_angle_degrees = Angle
-            .from_degrees(BigDecimal("360") - hour_angle_degrees)
+            .from_degrees(360 - hour_angle_degrees)
             .degrees
         end
 

diff --git a/lib/astronoby/geocentric_parallax.rb b/lib/astronoby/geocentric_parallax.rb
@@ -9,8 +9,8 @@ class GeocentricParallax
     #  Chapter: 39 - Calculating correction for parallax
 
     ASTRONOMICAL_UNIT_IN_METERS = 149_597_870_700
-    EARTH_FLATTENING_CORRECTION = BigDecimal("0.996647")
-    EARTH_EQUATORIAL_RADIUS = BigDecimal("6378140")
+    EARTH_FLATTENING_CORRECTION = 0.996647
+    EARTH_EQUATORIAL_RADIUS = 6378140.0
 
     # Equatorial horizontal parallax
     # @param distance [Numeric] Distance of the body from the center of the

diff --git a/lib/astronoby/observer.rb b/lib/astronoby/observer.rb
@@ -3,12 +3,12 @@
 module Astronoby
   class Observer
     DEFAULT_ELEVATION = 0
-    DEFAULT_TEMPERATURE = BigDecimal("283.15")
-    PRESSURE_AT_SEA_LEVEL = BigDecimal("1013.25")
-    PASCAL_PER_MILLIBAR = BigDecimal("0.01")
-    EARTH_GRAVITATIONAL_ACCELERATION = BigDecimal("9.80665")
-    MOLAR_MASS_OF_AIR = BigDecimal("0.0289644")
-    UNIVERSAL_GAS_CONSTANT = BigDecimal("8.31432")
+    DEFAULT_TEMPERATURE = 283.15
+    PRESSURE_AT_SEA_LEVEL = 1013.25
+    PASCAL_PER_MILLIBAR = 0.01
+    EARTH_GRAVITATIONAL_ACCELERATION = 9.80665
+    MOLAR_MASS_OF_AIR = 0.0289644
+    UNIVERSAL_GAS_CONSTANT = 8.31432
 
     attr_reader :latitude, :longitude, :elevation, :temperature
 
@@ -37,7 +37,7 @@ def initialize(
     # Compute an estimation of the atmospheric pressure based on the elevation
     # and temperature
     #
-    # @return [BigDecimal] the atmospheric pressure in millibars.
+    # @return [Float] the atmospheric pressure in millibars.
     def pressure
       @pressure ||= PRESSURE_AT_SEA_LEVEL * pressure_ratio
     end

diff --git a/lib/astronoby/time/greenwich_sidereal_time.rb b/lib/astronoby/time/greenwich_sidereal_time.rb
@@ -3,9 +3,9 @@
 module Astronoby
   class GreenwichSiderealTime
     JULIAN_CENTURIES_EXPONENTS = [
-      BigDecimal("6.697374558"),
-      BigDecimal("2400.051336"),
-      BigDecimal("0.000025862")
+      6.697374558,
+      2400.051336,
+      0.000025862
     ].freeze
 
     attr_reader :date, :time
@@ -29,7 +29,7 @@ def self.from_utc(utc)
         utc.min / 60.0 +
         (utc.sec + utc.subsec) / 3600.0
 
-      gmst = BigDecimal("1.002737909") * ut_in_hours + t0
+      gmst = 1.002737909 * ut_in_hours + t0
       gmst += 24 if gmst.negative?
       gmst -= 24 if gmst > 24
 
@@ -61,7 +61,7 @@ def to_utc
       a += 24 if a.negative?
       a -= 24 if a > 24
 
-      utc = BigDecimal("0.9972695663") * a
+      utc = 0.9972695663 * a
 
       decimal_hour_to_time(date, utc)
     end

diff --git a/lib/astronoby/util/trigonometry.rb b/lib/astronoby/util/trigonometry.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "bigdecimal/math"
-
 module Astronoby
   module Util
     module Trigonometry