Add binding for GHCJS

implement javascript versions under the assumption that engines where we run the code
will have V8 compatibile implementation. NodeJS looks fine.

double-conversion.cabal

@@ -70,6 +70,8 @@ library
     double-conversion/src/fast-dtoa.cc
     double-conversion/src/fixed-dtoa.cc
     double-conversion/src/strtod.cc
+  js-sources:
+     jsbits/hs-double-conversion.js
 
   if os(windows)
     if arch(x86_64)

jsbits/hs-double-conversion.js

@@ -0,0 +1,119 @@
+
+var kToFixedLength =
+  1 + /* DoubleToStringConverter::kMaxFixedDigitsBeforePoint*/ 60 +
+  1 + /* DoubleToStringConverter::kMaxFixedDigitsAfterPoint*/ 60;
+
+
+var kToShortestLength = 26;
+var kToExponentialLength =  /*DoubleToStringConverter::kMaxExponentialDigits*/ 120 + 8;
+var kToPrecisionLength =  /*DoubleToStringConverter::kMaxPrecisionDigits*/ 120 + 7;
+
+function h$_hs_ToShortestLength() {
+  return kToShortestLength;
+}
+
+function h$_hs_ToFixedLength()
+{
+  return kToFixedLength;
+}
+
+function h$_hs_ToExponentialLength()
+{
+  return kToExponentialLength;
+}
+
+function h$_hs_ToPrecisionLength()
+{
+  return kToPrecisionLength;
+}
+
+//--------------------
+
+function h$_hs_Text_ToShortest(value, buf)
+{
+ var conv = value.toString().replace("e+","e");
+ Array.prototype.map.call(conv,function(c,i){ buf.u1[i]=c.charCodeAt(0)});
+ return buf.len = conv.length;
+}
+
+function h$_hs_ToShortest(value, buf)
+{
+ var conv = value.toString().replace("e+","e");
+ Array.prototype.map.call(conv,function(c,i){ buf.u8[i]=c.charCodeAt(0)});
+ return buf.len = conv.length;
+}
+
+//--------------------
+
+function h$_hs_Text_ToFixed(value, buf, ndigits)
+{
+ // negative digits differ for small values
+  if (ndigits > 60) return -1;
+  if (ndigits > 0)
+  {
+    var conv = value.toFixed(Math.min(20,ndigits))+ "0".repeat(Math.max(0,ndigits - 20));
+    Array.prototype.map.call(conv,function(c,i){ buf.u1[i]=c.charCodeAt(0)});
+    return buf.len = conv.length;
+  }
+  else
+  {
+    var conv = value.toFixed(0).slice(0,ndigits) + "0".repeat(-ndigits);
+    Array.prototype.map.call(conv,function(c,i){ buf.u1[i]=c.charCodeAt(0)});
+    return buf.len = conv.length;
+  }
+}
+
+function h$_hs_ToFixed(value, buf, unused, ndigits)
+{
+ // negative digits differ for small values
+  if (ndigits > 60) return -1;
+  if (ndigits > 0)
+  {
+    var conv = value.toFixed(Math.min(20,ndigits))+ "0".repeat(Math.max(0,ndigits - 20));
+    Array.prototype.map.call(conv,function(c,i){ buf.u8[i]=c.charCodeAt(0)});
+    return buf.len = conv.length;
+  }
+  else
+  {
+    var conv = value.toFixed(0).slice(0,ndigits) + "0".repeat(-ndigits);
+    Array.prototype.map.call(conv,function(c,i){ buf.u8[i]=c.charCodeAt(0)});
+    return buf.len = conv.length;
+  }
+}
+
+//--------------------
+
+function h$_hs_Text_ToExponential(value, buf, ndigits)
+{
+
+ if (ndigits > 120 || ndigits < -1) return -1;
+ var conv = (ndigits == -1 ? value.toExponential() : value.toExponential(Math.min(20,ndigits)).replace("e",("0".repeat(Math.max(0,ndigits - 20))+"e"))).replace("e+","e");
+ Array.prototype.map.call(conv,function(c,i){ buf.u1[i]=c.charCodeAt(0)});
+ return buf.len = conv.length;
+}
+
+function h$_hs_ToExponential(value, buf, unused, ndigits)
+{
+ if (ndigits > 120 || ndigits < -1) return -1;
+ var conv = (ndigits == -1 ? value.toExponential() : value.toExponential(Math.min(20,ndigits)).replace("e",("0".repeat(Math.max(0,ndigits - 20))+"e"))).replace("e+","e");
+ Array.prototype.map.call(conv,function(c,i){ buf.u8[i]=c.charCodeAt(0)});
+ return buf.len = conv.length;
+}
+
+//--------------------
+
+function h$_hs_Text_ToPrecision(value, buf, ndigits)
+{
+  if (ndigits > 120 || ndigits < 1) return -1;
+  var conv = (value.toPrecision(Math.min(21,ndigits))+ "0".repeat(Math.max(0,ndigits - 21))).replace("e+","e");
+  Array.prototype.map.call(conv,function(c,i){ buf.u1[i]=c.charCodeAt(0)});
+  return buf.len = conv.length;
+}
+
+function h$_hs_ToPrecision(value, buf, unused, ndigits)
+{
+  if (ndigits > 120 || ndigits < 1) return -1;
+  var conv = (value.toPrecision(Math.min(21,ndigits))+ "0".repeat(Math.max(0,ndigits - 21))).replace("e+","e");
+  Array.prototype.map.call(conv,function(c,i){ buf.u8[i]=c.charCodeAt(0)});
+  return buf.len = conv.length;
+}