lib/measured/unit_system_builder.rb in measured-2.0.0 vs lib/measured/unit_system_builder.rb in measured-2.1.0

@@ -6,14 +6,51 @@
   def unit(unit_name, aliases: [], value: nil)
     @units << build_unit(unit_name, aliases: aliases, value: value)
     nil
   end
 
+  def si_unit(unit_name, aliases: [], value: nil)
+    @units += build_si_units(unit_name, aliases: aliases, value: value)
+    nil
+  end
+
   def build
     Measured::UnitSystem.new(@units)
   end
 
   private
+
+  SI_PREFIXES = [
+    ["y", "yocto", -24],
+    ["z", "zepto", -21],
+    ["a", "atto", -18],
+    ["f", "femto", -15],
+    ["p", "pico", -12],
+    ["n", "nano", -9],
+    ["μ", "micro", -6],
+    ["m", "milli", -3],
+    ["c", "centi", -2],
+    ["d", "deci", -1],
+    ["da", "deca", 1],
+    ["h", "hecto", 2],
+    ["k", "kilo", 3],
+    ["M", "mega", 6],
+    ["G", "giga", 9],
+    ["T", "tera", 12],
+    ["P", "peta", 15],
+    ["E", "exa", 18],
+    ["Z", "zetta", 21],
+    ["Y", "yotta", 24]
+  ]
+
+  def build_si_units(name, aliases: [], value: nil)
+    si_units = [build_unit(name, aliases: aliases, value: value)]
+    SI_PREFIXES.each do |short, long, exp|
+      long_names = aliases.map { |suffix| "#{long}#{suffix}" }
+      si_units << build_unit("#{short}#{name}", aliases: long_names, value: "#{10 ** exp} #{name}")
+    end
+    si_units
+  end
 
   def build_unit(name, aliases: [], value: nil)
     unit = Measured::Unit.new(name, aliases: aliases, value: value)
     check_for_duplicate_unit_names!(unit)
     unit