Make fltXYexplode and fltXYassem inverses of each other

The exponent and significand (mantissa) returned from fltXYexplode
are the numerical values, not just the bit patterns. Informally,

    flt64explode(1.23 x 10^101)

would return (false, 123000..., 101), where the significand has
precisely 52 bits after the intial `1'.

2 files changed, 64 insertions, 0 deletions

diff --git a/lib/std/test/fltbits.myr b/lib/std/test/fltbits.myr
index 6e3b7c3..1354c70 100644
--- a/lib/std/test/fltbits.myr
+++ b/lib/std/test/fltbits.myr
@@ -9,6 +9,8 @@ const main = {
 		[.name = "bits-roundtrip-64", .fn = bitsround64],
 		[.name = "flt32bits", .fn = flt32bits],
 		[.name = "flt64bits", .fn = flt64bits],
+		[.name = "explode-roundtrip-32", .fn = exploderound32],
+		[.name = "explode-roundtrip-64", .fn = exploderound64],
 	][:])
 }
 
@@ -96,3 +98,64 @@ const flt64bits = {c
 		testr.check(c, u == uprime, "flt64bits wrong for {}:  0x{x} != 0x{x}", f, u, uprime)
 	;;
 }
+
+const exploderound32 = {c
+	for f : [1.0, 0.00001, 123.45, 1111111111111111.2, -1.9, -0.0001, std.flt32nan()][:]
+		var n, e, s
+		(n, e, s) = std.flt32explode(f)
+		var g = std.flt32assem(n, e, s)
+		testr.check(c, f == g, "assem o explode non-identity: {} != {}", f, g)
+	;;
+
+	/*
+	   The exponents and significands need to be rather specific
+	   in order for flt32assem to work as expected
+	 */
+	for (n, e, s) : [
+			(false, 0, -127),
+			(true, 0, -127),
+			(false, 0x399, -127),
+			(true, 0x23, -127),
+			(false, (1 << 23) | 0x23, 45),
+			(true, (1 << 23) | 0x3a2, -12),
+			(true, (1 << 23) | 0x3a1, -126),
+		][:]
+		var m, f, t
+		(m, f, t) = std.flt32explode(std.flt32assem(n, e, s))
+		testr.check(c, n == m, "explode o assem non-identity: {} != {}", (n, e, s), (m, f, t))
+		testr.check(c, e == f, "explode o assem non-identity: {} != {}", (n, e, s), (m, f, t))
+		testr.check(c, s == t, "explode o assem non-identity: {} != {}", (n, e, s), (m, f, t))
+	;;
+}
+
+const exploderound64 = {c
+	for f : [1.0, 0.00001, 123.45, 1111111111111e+309, -1.9, -0.0001, std.flt64nan()][:]
+		var n, e, s
+		(n, e, s) = std.flt64explode(f)
+		var g = std.flt64assem(n, e, s)
+		testr.check(c, f == g, "assem o explode non-identity: {} != {}", f, g)
+	;;
+
+	/*
+	   The exponents and significands need to be rather specific
+	   in order for flt32assem to work as expected
+	 */
+	for (n, e, s) : [
+			(false, 0, -1023),
+			(true, 0, -1023),
+			(false, 0x399, -1023),
+			(true, 0x23, -1023),
+			(false, (1 << 52) | 0xa33bc, 45),
+			(true, (1 << 52) | 0x3, -12),
+			(true, (1 << 52) | 0x11aabbcc, -200),
+			(true, (1 << 52) | 0x3a1, 543),
+			(true, (1 << 52) | 0x99aa228, 1001),
+		][:]
+		var m, f, t
+		(m, f, t) = std.flt64explode(std.flt64assem(n, e, s))
+		testr.check(c, n == m, "explode o assem non-identity: {} != {}", (n, e, s), (m, f, t))
+		testr.check(c, e == f, "explode o assem non-identity: {} != {}", (n, e, s), (m, f, t))
+		testr.check(c, s == t, "explode o assem non-identity: {} != {}", (n, e, s), (m, f, t))
+	;;
+}
+
diff --git a/lib/std/test/fmt.myr b/lib/std/test/fmt.myr
index da1b76a..acf499f 100644
--- a/lib/std/test/fmt.myr
+++ b/lib/std/test/fmt.myr
@@ -66,6 +66,7 @@ const builtins = {
 	check("7b", "{x}", 123)
 	check("0x7b", "0x{x}", 123)
 	check("0.0", "{}", 0.0)
+	check("-0.0", "{}", -0.0)
 	check("0.3", "{}", 0.3)
 	check("0.3", "{}", (0.3 : flt32))
 	check("1.0", "{}", 1.0)