Merge pull request jruby#9045 from enebo/topic/fix_9044

Fixes basic float hex value strings for Kernel#Float

Author: enebo

core/src/main/java/org/jruby/RubyKernel.java

@@ -420,8 +420,6 @@ public static RubyFloat new_float(IRubyObject recv, IRubyObject object) {
         return (RubyFloat) new_float(recv.getRuntime().getCurrentContext(), object, true);
     }
 
-    private static final ByteList ZEROx = new ByteList(new byte[] { '0','x' }, false);
-
     public static RubyFloat new_float(final Ruby runtime, IRubyObject object) {
         return (RubyFloat) new_float(runtime.getCurrentContext(), object, true);
     }
@@ -540,7 +538,7 @@ public static IRubyObject new_float(ThreadContext context, IRubyObject object, b
                 throw runtime.newArgumentError("invalid value for Float(): " + object.inspect());
             }
 
-            if (bytes.startsWith(ZEROx)) { // startsWith("0x")
+            if (isHexValue(bytes)) {
                 if (bytes.indexOf('p') != -1 || bytes.indexOf('P') != -1) {
                     return runtime.newFloat(parseHexidecimalExponentString2(runtime, bytes));
                 }
@@ -567,6 +565,12 @@ public static IRubyObject new_float(ThreadContext context, IRubyObject object, b
         return TypeConverter.handleUncoercibleObject(runtime, object, runtime.getFloat(), true);
     }
 
+    static boolean isHexValue(ByteList bytes) {
+        int length = bytes.getRealSize();
+        int index = length >= 1 && bytes.get(0) == '-' ? 1 : 0;
+        return length >= index + 2 && bytes.get(index) == '0' && (bytes.get(index + 1) == 'x' || bytes.get(index + 1) == 'X');
+    }
+
     static RubyFloat new_float(final Ruby runtime, RubyInteger num) {
         if (num instanceof RubyBignum) {
             return RubyFloat.newFloat(runtime, RubyBignum.big2dbl((RubyBignum) num));

spec/ruby/core/kernel/Float_spec.rb

@@ -222,6 +222,18 @@ def to_f() 1.2 end
     end
   end
 
+  describe "for hexidecimal literals" do
+    it "interprets positive hex value" do
+      @object.send(:Float, "0x10").should == 16.0
+      @object.send(:Float, "0X10").should == 16.0
+    end
+
+    it "interprets negative hex value" do
+      @object.send(:Float, "-0x10").should == -16.0
+      @object.send(:Float, "-0X10").should == -16.0
+    end
+  end
+
   describe "for hexadecimal literals with binary exponent" do
     %w(p P).each do |p|
       it "interprets the fractional part (on the left side of '#{p}') in hexadecimal" do