Explores whether unsigned 64-bit integers can reuse the same per-target Int64Native implementation as signed Int64, avoiding native code duplication. Answer: yes, with minimal complications.

Design

• haxe.UInt64 — abstract UInt64(Int64Native) wrapping the same backing type as Int64
• Bit-identical ops (add, sub, mul, bitwise, shl) delegate directly to Int64Native
• Unsigned-specific ops are added to Int64Native itself (udivMod, utoString, uparseString, ufromFloat, utoFloat) on all targets, so native targets can provide optimized implementations in the future. The portable algorithms live in haxe.numeric.UInt64Helper and are used as the default implementation.
• Comparison uses existing Int64Native.ucompare; >> maps to existing Int64Native.ushr
• UInt64 has only toString() (no redundant toStr static method)

Key unsigned behaviors

var a = UInt64.make(0x80000000, 0); // 2^63
var b = UInt64.make(0x7FFFFFFF, 0xFFFFFFFF); // 2^63 - 1
trace(a > b); // true (signed Int64 would say false)
trace(Std.string(a)); // "9223372036854775808"

var max = UInt64.make(0xFFFFFFFF, 0xFFFFFFFF);
trace(max >> 4); // logical shift, no sign extension
trace(Std.string(max / 2)); // "9223372036854775807"

Int64 vs UInt64 public interface comparison

Only in Int64: isNeg, ucompare, toStr, isInt64, getHigh/getLow (deprecated), is (deprecated)

Only in UInt64: toFloat, fromInt64, toInt64

Same method, different semantics: compare (signed vs unsigned), toInt (throws vs truncates), toString (signed vs unsigned decimal), parseString/fromFloat (signed vs unsigned range), divMod/div/mod (signed vs unsigned division), shr (>>) (arithmetic vs logical shift)

Identical in both: copy, make, ofInt, isZero, add, sub, mul, eq, neq, and, or, xor, shl, ushr, neg, high/low properties

Files changed

• std/haxe/UInt64.hx — public abstract with operator overloads, all ops route through Int64Native
• std/haxe/numeric/UInt64Helper.hx — portable unsigned algorithms (division, toString, parsing, float conversion)
• std/haxe/numeric/Int64Native.hx — added udivMod, utoString, uparseString, ufromFloat, utoFloat
• std/jvm/_std/haxe/numeric/Int64Native.hx — added unsigned method signatures (delegates to UInt64Helper)
• std/hl/_std/haxe/numeric/Int64Native.hx — added unsigned method signatures (delegates to UInt64Helper)
• std/cpp/_std/haxe/numeric/Int64Native.hx — added unsigned method signatures with CPPIA declarations
• std/eval/_std/haxe/numeric/Int64Native.hx — added unsigned method signatures (delegates to UInt64Helper)
• tests/unit/src/unit/TestUInt64.hx — covers construction, unsigned comparison/division/shifts, Int64 round-trips, parsing, edge cases

All unit tests pass on Interp, JS, JVM, Python, Neko, PHP.

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