Fix printing of zero BigDecimals

Author: chrisseaton

lib/truffle/bigdecimal.rb

@@ -207,7 +207,13 @@ def frac
   end
 
   def to_s(format = 'E')
-    if finite?
+    if zero?
+      if sign == SIGN_NEGATIVE_ZERO
+        '-0.0'
+      else
+        '0.0'
+      end
+    elsif finite?
       float_format    = format[-1] == 'F' || format[-1] == 'f'
       space_frequency = format.to_i
       prefix          = if self > 0 && [' ', '+'].include?(format[0])

spec/ruby/library/bigdecimal/inspect_spec.rb

@@ -15,6 +15,12 @@
     @bigdec.inspect.should == "0.12345678e4"
   end
 
+  it "does not add an exponent for zero values" do
+    BigDecimal("0").inspect.should == "0.0"
+    BigDecimal("+0").inspect.should == "0.0"
+    BigDecimal("-0").inspect.should == "-0.0"
+  end
+
   it "properly cases non-finite values" do
     BigDecimal("NaN").inspect.should == "NaN"
     BigDecimal("Infinity").inspect.should == "Infinity"

spec/ruby/library/bigdecimal/to_s_spec.rb

@@ -19,6 +19,12 @@
     @bigdec.to_s.should =~ /^0\.[0-9]*e[0-9]*$/
   end
 
+  it "does not add an exponent for zero values" do
+    BigDecimal("0").to_s.should == "0.0"
+    BigDecimal("+0").to_s.should == "0.0"
+    BigDecimal("-0").to_s.should == "-0.0"
+  end
+
   it "takes an optional argument" do
     lambda {@bigdec.to_s("F")}.should_not raise_error()
   end