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std.math: add support to cast for a comptime_int argument

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This allows converting a comptime_int to an optional integer type, which
either behaves the same as an implicit cast or produces null if the
argument is outside the range of the destination type.
This commit is contained in:
Jacob Young 2022-09-20 22:46:42 -04:00
parent e6ebdcb82e
commit 7a89eebfc6
1 changed files with 10 additions and 3 deletions
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13
lib/std/math.zig
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@ -1062,10 +1062,11 @@ test "negateCast" {
/// return null.
pub fn cast(comptime T: type, x: anytype) ?T {
comptime assert(@typeInfo(T) == .Int); // must pass an integer
comptime assert(@typeInfo(@TypeOf(x)) == .Int); // must pass an integer
if (maxInt(@TypeOf(x)) > maxInt(T) and x > maxInt(T)) {
const is_comptime = @TypeOf(x) == comptime_int;
comptime assert(is_comptime or @typeInfo(@TypeOf(x)) == .Int); // must pass an integer
if ((is_comptime or maxInt(@TypeOf(x)) > maxInt(T)) and x > maxInt(T)) {
return null;
} else if (minInt(@TypeOf(x)) < minInt(T) and x < minInt(T)) {
} else if ((is_comptime or minInt(@TypeOf(x)) < minInt(T)) and x < minInt(T)) {
return null;
} else {
return @intCast(T, x);
@ -1073,12 +1074,18 @@ pub fn cast(comptime T: type, x: anytype) ?T {
}
test "cast" {
try testing.expect(cast(u8, 300) == null);
try testing.expect(cast(u8, @as(u32, 300)) == null);
try testing.expect(cast(i8, -200) == null);
try testing.expect(cast(i8, @as(i32, -200)) == null);
try testing.expect(cast(u8, -1) == null);
try testing.expect(cast(u8, @as(i8, -1)) == null);
try testing.expect(cast(u64, -1) == null);
try testing.expect(cast(u64, @as(i8, -1)) == null);
try testing.expect(cast(u8, 255).? == @as(u8, 255));
try testing.expect(cast(u8, @as(u32, 255)).? == @as(u8, 255));
try testing.expect(@TypeOf(cast(u8, 255).?) == u8);
try testing.expect(@TypeOf(cast(u8, @as(u32, 255)).?) == u8);
}