add bigdecimal

spec/pg/numeric_spec.cr

@@ -1,5 +1,6 @@
 require "../spec_helper"
 require "../../src/pg_ext/big_rational"
+require "../../src/pg_ext/big_decimal"
 
 private def n(nd, w, s, ds, d)
   PG::Numeric.new(nd.to_i16, w.to_i16, s.to_i16, ds.to_i16, d.map(&.to_i16))
@@ -9,6 +10,10 @@ private def br(n, d)
   BigRational.new(n, d)
 end
 
+private def bd(d)
+  BigDecimal.new(d)
+end
+
 private def ex(which)
   case which
   when "nan"
@@ -82,6 +87,24 @@ describe PG::Numeric do
     end
   end
 
+  it "to_big_d" do
+    [
+      {"nan", bd(0)},
+      {"0", bd(0)},
+      {"0.0", bd(0)},
+      {"1", bd(1)},
+      {"-1", bd(-1)},
+      {"1.30", bd(1.3)},
+      {"12345.6789123", bd(12345.6789123)},
+      {"-0.00009", bd(-0.00009)},
+      {"-0.000009", bd(-0.000009)},
+      {"-0.0000009", bd(-0.0000009)},
+      {"-0.00000009", bd(-0.00000009)},
+    ].each do |x|
+      ex(x[0]).to_big_d.should eq(x[1])
+    end
+  end
+
   it "#to_s" do
     [
       {"nan", "NaN"},

src/pg_ext/big_decimal.cr

@@ -0,0 +1,23 @@
+require "big"
+
+module PG
+  struct Numeric
+    # Returns a BigDecimal representation of the numeric. This retains all precision.
+    def to_big_d
+      return BigDecimal.new("0") if nan? || ndigits == 0
+
+      # Since BigDecimal allows initialaztion from String, why should one reinvent the wheel?
+      BigDecimal.new(to_s)
+    end
+  end
+
+  class ResultSet
+    def read(t : BigDecimal.class)
+      read(PG::Numeric).to_big_d
+    end
+
+    def read(t : BigDecimal?.class)
+      read(PG::Numeric?).try &.to_big_d
+    end
+  end
+end