fix: std.primitiveEquals(-0.0, 0.0) should return true

[He-Pin]

Summary

Fix std.primitiveEquals(-0.0, 0.0) to return true (IEEE 754 semantics), matching go-jsonnet and C++ jsonnet behavior.

Changes

• sjsonnet/src/sjsonnet/stdlib/TypeModule.scala: Change primitiveEquals for numbers from ev.compare(x, y) == 0 to x.rawDouble == y.rawDouble
• Add test case: test/resources/new_test_suite/primitive_equals_negative_zero.jsonnet

Implementation Comparison

Implementation	Code	-0.0 == 0.0	Performance
go-jsonnet	left.value == right.value	true	Fast (direct ==)
jrsonnet	(a.get() - b.get()).abs() <= f64::EPSILON	true	Slower (subtraction + abs)
sjsonnet (original)	ev.compare(x, y) == 0	false ❌	Slow (method call + Double.compare)
sjsonnet (this PR)	x.rawDouble == y.rawDouble	true ✅	Fast (direct ==)

Performance Analysis

Current implementation (ev.compare(x, y) == 0)

// Evaluator.scala:2038
def compare(x: Val, y: Val): Int = (x, y) match {
  case (x: Val.Num, y: Val.Num) => java.lang.Double.compare(x.asDouble, y.asDouble)
  ...
}

• Method call overhead
• java.lang.Double.compare distinguishes -0.0 and 0.0 (returns -1)
• asDouble has NaN check overhead

New implementation (x.rawDouble == y.rawDouble)

// TypeModule.scala
case (x: Val.Num, y: Val.Num) =>
  x.rawDouble == y.rawDouble

• Direct field access
• Direct == operator
• No method call overhead
• Consistent with go-jsonnet

jrsonnet implementation

(Val::Num(a), Val::Num(b)) => (a.get() - b.get()).abs() <= f64::EPSILON,

• Subtraction + abs + comparison
• More expensive than direct ==

Why this change is correct

1. IEEE 754 semantics: -0.0 == 0.0 is true per IEEE 754
2. Consistency with references: go-jsonnet and C++ jsonnet both treat -0.0 and 0.0 as equal
3. Performance: Direct == is faster than method call + Double.compare
4. rawDouble is safe: NaN cannot arise from valid Jsonnet expressions (constructor guards against infinity, no standard operator produces NaN)

Test

// test/resources/new_test_suite/primitive_equals_negative_zero.jsonnet
std.assertEqual(std.primitiveEquals(-0.0, 0.0), true) &&
std.assertEqual(std.primitiveEquals(0.0, -0.0), true) &&
std.assertEqual(std.primitiveEquals(-0.0, -0.0), true) &&
std.assertEqual(std.primitiveEquals(0.0, 0.0), true) &&
std.assertEqual(std.primitiveEquals(-0.0, 1.0), false) &&
std.assertEqual(std.primitiveEquals(0.0, 1.0), false) &&
true