Merge pull request #5 from shivam091/1.4.0

1.4.0

CHANGELOG.md

@@ -1,3 +1,11 @@
+## [1.4.0](https://github.com/shivam091/unit_measurements/compare/v1.3.0...v1.4.0) - 2023-08-17
+
+### What's new
+
+- Added ability to perform `arithmetic` operations of measurements.
+
+----------
+
 ## [1.3.0](https://github.com/shivam091/unit_measurements/compare/v1.2.0...v1.3.0) - 2023-08-16
 
 ### What's new

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    unit_measurements (1.3.0)
+    unit_measurements (1.4.0)
       activesupport (~> 7.0)
 
 GEM

README.md

@@ -322,6 +322,29 @@ UnitMeasurements::Weight.parse("1 kg") >= UnitMeasurements::Weight.parse("0.5 kg
 #=> true
 ```
 
+### Arithmetic
+
+You have the ability to perform arithmetic operations on measurements with the same or
+different units within the same unit group. You can perform arithmetic operations on
+measurement by either other compatible measurement or number.
+
+**Methods:**
+1. `#+` - Adds the other measurement quantity or number to the measurement.
+2. `#-` - Subtracts the other measurement quantity or number from the measurement.
+3. `#*` - Multiplies the measurement quantity by other measurement quantity or number.
+4. `#/` - Divides the measurement quantity by other measurement quantity or number.
+
+```ruby
+UnitMeasurements::Weight.new(1, :kg) + UnitMeasurements::Weight.new(1, :g)
+#=> 1.001 kg
+UnitMeasurements::Weight.new(2, :kg) - 1
+#=> 1 kg
+UnitMeasurements::Weight.new(2, :kg) * 2
+#=> 4 kg
+UnitMeasurements::Weight.new(4, :kg) / UnitMeasurements::Weight.new(2, :kg)
+#=> 2 kg
+```
+
 ## Units
 
 The **`UnitMeasurements::Unit`** class is used to represent the units for a measurement.

lib/unit_measurements/arithmetic.rb

@@ -0,0 +1,74 @@
+# -*- encoding: utf-8 -*-
+# -*- frozen_string_literal: true -*-
+# -*- warn_indent: true -*-
+
+module UnitMeasurements
+  module Arithmetic
+    # Adds the other measurement quantity or number to the measurement.
+    #
+    # @param [Numeric or Measurement] other
+    #
+    # @example
+    #   UnitMeasurements::Weight.new(1, :kg) + UnitMeasurements::Weight.new(1, :g)
+    #   => 1.001 kg
+    #
+    # @return [Measurement]
+    def +(other)
+      arithmetic_operation(other, :+)
+    end
+
+    # Subtracts the other measurement quantity or number from the measurement.
+    #
+    # @param [Numeric or Measurement] other
+    #
+    # @example
+    #   UnitMeasurements::Weight.new(2, :kg) - 1
+    #   => 1 kg
+    #
+    # @return [Measurement]
+    def -(other)
+      arithmetic_operation(other, :-)
+    end
+
+    # Multiplies the measurement quantity by other measurement quantity or number.
+    #
+    # @param [Numeric or Measurement] other
+    #
+    # @example
+    #   UnitMeasurements::Weight.new(2, :kg) * 2
+    #   => 4 kg
+    #
+    # @return [Measurement]
+    def *(other)
+      arithmetic_operation(other, :*)
+    end
+
+    # Divides the measurement quantity by other measurement quantity or number.
+    #
+    # @param [Numeric or Measurement] other
+    #
+    # @example
+    #   UnitMeasurements::Weight.new(4, :kg) / UnitMeasurements::Weight.new(2, :kg)
+    #   => 2 kg
+    #
+    # @return [Measurement]
+    def /(other)
+      arithmetic_operation(other, :/)
+    end
+
+    private
+
+    def coerce(other)
+      case other
+      when Numeric    then [self.class.new(other, self.unit), self]
+      when self.class then [other, self]
+      else                 raise TypeError, "Cannot coerce #{other.class} to #{self.class}"
+      end
+    end
+
+    def arithmetic_operation(other, operator)
+      other, _ = coerce(other)
+      self.class.new(self.quantity.public_send(operator, other.convert_to(self.unit).quantity), self.unit)
+    end
+  end
+end

lib/unit_measurements/base.rb

@@ -25,10 +25,11 @@ class << self
 require "unit_measurements/unit_group_builder"
 require "unit_measurements/unit"
 require "unit_measurements/unit_group"
+require "unit_measurements/arithmetic"
+require "unit_measurements/comparison"
 require "unit_measurements/normalizer"
 require "unit_measurements/parser"
 require "unit_measurements/formatter"
-require "unit_measurements/comparison"
 require "unit_measurements/measurement"
 
 require "unit_measurements/errors/unit_error"

lib/unit_measurements/measurement.rb

@@ -6,6 +6,7 @@ module UnitMeasurements
   class Measurement
     include Formatter
     include Comparison
+    include Arithmetic
 
     CONVERSION_STRING_REGEXP = /(.+?)\s?(?:\s+(?:in|to|as)\s+(.+)|\z)/i.freeze
 

lib/unit_measurements/version.rb

@@ -3,5 +3,5 @@
 # -*- warn_indent: true -*-
 
 module UnitMeasurements
-  VERSION = "1.3.0"
+  VERSION = "1.4.0"
 end

spec/unit_measurements/arithmetic_spec.rb

@@ -0,0 +1,107 @@
+# -*- encoding: utf-8 -*-
+# -*- frozen_string_literal: true -*-
+# -*- warn_indent: true -*-
+
+# spec/unit_measurements/arithmetic_spec.rb
+
+RSpec.describe UnitMeasurements::Arithmetic do
+  subject { UnitMeasurements::Length }
+  let(:m) { subject.unit_for!(:m) }
+  let(:cm) { subject.unit_for!(:cm) }
+
+  describe "#+" do
+    it "must add numbers" do
+      measurement = subject.new(3.5, :m) + 2
+      expect(measurement.quantity).to eq(5.5)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must add similar units" do
+      measurement = (subject.new(3.5, :m) + subject.new(2, :m))
+      expect(measurement.quantity).to eq(5.5)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must add unsimilar units" do
+      measurement = (subject.new(3.5, :cm) + subject.new(2, :m))
+      expect(measurement.quantity).to eq(203.5)
+      expect(measurement.unit).to eq(cm)
+    end
+  end
+
+  describe "#-" do
+    it "must subtract numbers" do
+      measurement = (subject.new(3.5, :m) - 2)
+      expect(measurement.quantity).to eq(1.5)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must subtract unsimilar units" do
+      measurement = (subject.new(3.5, :m) - subject.new(2, :m))
+      expect(measurement.quantity).to eq(1.5)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must subtract similar units" do
+      measurement = (subject.new(3.5, :m) - subject.new(2, :cm))
+      expect(measurement.quantity).to eq(3.48)
+      expect(measurement.unit).to eq(m)
+    end
+  end
+
+  describe "#*" do
+    it "must multiply by numbers" do
+      measurement = (subject.new(3.5, :m) * 2)
+      expect(measurement.quantity).to eq(7)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must multiply by similar units" do
+      measurement = (subject.new(3.5, :m) * subject.new(2, :m))
+      expect(measurement.quantity).to eq(7)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must multiply by unsimilar units" do
+      measurement = (subject.new(3.5, :m) * subject.new(2, :cm))
+      expect(measurement.quantity).to eq(0.07)
+      expect(measurement.unit).to eq(m)
+    end
+  end
+
+  describe "#/" do
+    it "must divide by numbers" do
+      measurement = (subject.new(4, :m) / 2)
+      expect(measurement.quantity).to eq(2)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must divide by similar units" do
+      measurement = (subject.new(4, :m) / subject.new(2, :m))
+      expect(measurement.quantity).to eq(2)
+      expect(measurement.unit).to eq(m)
+    end
+
+    it "must divide by unsimilar units" do
+      measurement = (subject.new(36, :cm) / subject.new(2, :m))
+      expect(measurement.quantity).to eq(0.18)
+      expect(measurement.unit).to eq(cm)
+    end
+  end
+
+  describe "#coerce" do
+    let(:meter) { subject.new(1, :m) }
+
+    it "must coerce numbers" do
+      expect((meter * 5).quantity).to eq(5)
+    end
+
+    it "must coerce measurements" do
+      expect((meter * subject.new(1, :cm)).quantity).to eq(0.01)
+    end
+
+    it "should raise an error for other than numbers and measurement instance" do
+      expect { meter * "foo" }.to raise_error(TypeError)
+    end
+  end
+end

spec/unit_measurements_spec.rb

@@ -4,6 +4,6 @@
 
 RSpec.describe UnitMeasurements do
   it "has a valid version number" do
-    expect(UnitMeasurements::VERSION).to eq("1.3.0")
+    expect(UnitMeasurements::VERSION).to eq("1.4.0")
   end
 end