Commit 62fe4a0ba8a08b9477e772841d3ae128937f0752 | zig

author	Justin Whear <justin.whear+github@gmail.com> 2021-08-19 12:18:23-07:00
committer	GitHub <noreply@github.com> 2021-08-19 22:18:23+03:00
log	62fe4a0ba8a08b9477e772841d3ae128937f0752
tree	763f892c896ceac7e45e6ba3408ccede4116a0e2
parent	7e7d67d8eed45bcf3908edd2f4ca864144fffad5
signature	Signed by PGP key 4AEE18F83AFDEB23

std.rand.Random: add enumValue() (#9583)

* add Random.enumValue()

* edits suggested by review

* applied zig fmt

* Rewrite to use std.enums.values

Implemented pfgithub's suggestion to rewrite against this function, greatly simplifying the implementation.

Co-authored-by: Justin Whear <justin@economicmodeling.com>

1 files changed, 30 insertions(+), 0 deletions(-)

lib
- std
  - rand.zig

lib/std/rand.zig+30

...	...	@@ -47,6 +47,19 @@ pub const Random = struct {
47	47	return r.int(u1) != 0;
48	48	}
49	49
	50	/// Returns a random value from an enum, evenly distributed.
	51	pub fn enumValue(r: *Random, comptime EnumType: type) EnumType {
	52	if (comptime !std.meta.trait.is(.Enum)(EnumType)) {
	53	@compileError("Random.enumValue requires an enum type, not a " ++ @typeName(EnumType));
	54	}
	55
	56	// We won't use int -> enum casting because enum elements can have
	57	// arbitrary values. Instead we'll randomly pick one of the type's values.
	58	const values = std.enums.values(EnumType);
	59	const index = r.uintLessThan(usize, values.len);
	60	return values[index];
	61	}
	62
50	63	/// Returns a random int `i` such that `0 <= i <= maxInt(T)`.
51	64	/// `i` is evenly distributed.
52	65	pub fn int(r: *Random, comptime T: type) T {
...	...	@@ -377,6 +390,23 @@ fn testRandomBoolean() !void {
377	390	try expect(r.random.boolean() == true);
378	391	}
379	392
	393	test "Random enum" {
	394	try testRandomEnumValue();
	395	comptime try testRandomEnumValue();
	396	}
	397	fn testRandomEnumValue() !void {
	398	const TestEnum = enum {
	399	First,
	400	Second,
	401	Third,
	402	};
	403	var r = SequentialPrng.init();
	404	r.next_value = 0;
	405	try expect(r.random.enumValue(TestEnum) == TestEnum.First);
	406	try expect(r.random.enumValue(TestEnum) == TestEnum.First);
	407	try expect(r.random.enumValue(TestEnum) == TestEnum.First);
	408	}
	409
380	410	test "Random intLessThan" {
381	411	@setEvalBranchQuota(10000);
382	412	try testRandomIntLessThan();