Commit 2baf0e2ffc154d7915e690ddb4d892d1bafd5db2 | zig

author	daurnimator <quae@daurnimator.com> 2018-11-26 21:12:16+11:00
committer	Andrew Kelley <andrew@ziglang.org> 2018-11-27 10:19:06-05:00
log	2baf0e2ffc154d7915e690ddb4d892d1bafd5db2
tree	f33add4650707feefdcae29dcf346a8e4911185d
parent	6bbe4cf9f7e0af4d3a15d42aece015792153c518

add std.math.IntFittingRange

1 files changed, 63 insertions(+), 0 deletions(-)

std
- math
  - index.zig

std/math/index.zig+63

...	@@ -365,6 +365,69 @@ pub fn Log2Int(comptime T: type) type {	...	@@ -365,6 +365,69 @@ pub fn Log2Int(comptime T: type) type {
365	return @IntType(false, count);	365	return @IntType(false, count);
366	}	366	}
367		367
		368	pub fn IntFittingRange(comptime from: comptime_int, comptime to: comptime_int) type {
		369	assert(from <= to);
		370	if (from == 0 and to == 0) {
		371	return u0;
		372	}
		373	const is_signed = from < 0;
		374	const largest_positive_integer = max(if (from<0) (-from)-1 else from, to); // two's complement
		375	const base = log2(largest_positive_integer);
		376	const upper = (1 << base) - 1;
		377	var magnitude_bits = if (upper >= largest_positive_integer) base else base + 1;
		378	if (is_signed) {
		379	magnitude_bits += 1;
		380	}
		381	return @IntType(is_signed, magnitude_bits);
		382	}
		383
		384	test "math.IntFittingRange" {
		385	assert(IntFittingRange(0, 0) == u0);
		386	assert(IntFittingRange(0, 1) == u1);
		387	assert(IntFittingRange(0, 2) == u2);
		388	assert(IntFittingRange(0, 3) == u2);
		389	assert(IntFittingRange(0, 4) == u3);
		390	assert(IntFittingRange(0, 7) == u3);
		391	assert(IntFittingRange(0, 8) == u4);
		392	assert(IntFittingRange(0, 9) == u4);
		393	assert(IntFittingRange(0, 15) == u4);
		394	assert(IntFittingRange(0, 16) == u5);
		395	assert(IntFittingRange(0, 17) == u5);
		396	assert(IntFittingRange(0, 4095) == u12);
		397	assert(IntFittingRange(2000, 4095) == u12);
		398	assert(IntFittingRange(0, 4096) == u13);
		399	assert(IntFittingRange(2000, 4096) == u13);
		400	assert(IntFittingRange(0, 4097) == u13);
		401	assert(IntFittingRange(2000, 4097) == u13);
		402	assert(IntFittingRange(0, 123456789123456798123456789) == u87);
		403	assert(IntFittingRange(0, 123456789123456798123456789123456789123456798123456789) == u177);
		404
		405	assert(IntFittingRange(-1, -1) == i1);
		406	assert(IntFittingRange(-1, 0) == i1);
		407	assert(IntFittingRange(-1, 1) == i2);
		408	assert(IntFittingRange(-2, -2) == i2);
		409	assert(IntFittingRange(-2, -1) == i2);
		410	assert(IntFittingRange(-2, 0) == i2);
		411	assert(IntFittingRange(-2, 1) == i2);
		412	assert(IntFittingRange(-2, 2) == i3);
		413	assert(IntFittingRange(-1, 2) == i3);
		414	assert(IntFittingRange(-1, 3) == i3);
		415	assert(IntFittingRange(-1, 4) == i4);
		416	assert(IntFittingRange(-1, 7) == i4);
		417	assert(IntFittingRange(-1, 8) == i5);
		418	assert(IntFittingRange(-1, 9) == i5);
		419	assert(IntFittingRange(-1, 15) == i5);
		420	assert(IntFittingRange(-1, 16) == i6);
		421	assert(IntFittingRange(-1, 17) == i6);
		422	assert(IntFittingRange(-1, 4095) == i13);
		423	assert(IntFittingRange(-4096, 4095) == i13);
		424	assert(IntFittingRange(-1, 4096) == i14);
		425	assert(IntFittingRange(-4097, 4095) == i14);
		426	assert(IntFittingRange(-1, 4097) == i14);
		427	assert(IntFittingRange(-1, 123456789123456798123456789) == i88);
		428	assert(IntFittingRange(-1, 123456789123456798123456789123456789123456798123456789) == i178);
		429	}
		430
368	test "math overflow functions" {	431	test "math overflow functions" {
369	testOverflow();	432	testOverflow();
370	comptime testOverflow();	433	comptime testOverflow();