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impl lossyCast #5080

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Adam Goertz 2020-10-27 22:55:12 -04:00 committed by Andrew Kelley
parent e1d8073d2f
commit 0f32de77c9
1 changed files with 34 additions and 6 deletions
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40
lib/std/math.zig
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@ -1070,16 +1070,44 @@ test "std.math.log2_int_ceil" {
testing.expect(log2_int_ceil(u32, 10) == 4);
}
///Cast a value to a different type. If the value doesn't fit in, or can't be perfectly represented by,
///the new type, it will be converted to the closest possible representation.
pub fn lossyCast(comptime T: type, value: anytype) T {
switch (@typeInfo(@TypeOf(value))) {
.Int => return @intToFloat(T, value),
.Float => return @floatCast(T, value),
.ComptimeInt => return @as(T, value),
.ComptimeFloat => return @as(T, value),
else => @compileError("bad type"),
switch(@typeInfo(T)) {
.Float => {
switch (@typeInfo(@TypeOf(value))) {
.Int => return @intToFloat(T, value),
.Float => return @floatCast(T, value),
.ComptimeInt => return @as(T, value),
.ComptimeFloat => return @as(T, value),
else => @compileError("bad type"),
}
},
.Int => {
switch(@typeInfo(@TypeOf(value))) {
.Int, .ComptimeInt => {
if (value > maxInt(T)) { return @as(T, maxInt(T)); }
else if (value < minInt(T)) { return @as(T, minInt(T)); }
else { return @intCast(T, value); }
},
.Float, .ComptimeFloat => {
if (value > maxInt(T)) { return @as(T, maxInt(T)); }
else if (value < minInt(T)) { return @as(T, minInt(T)); }
else { return @floatToInt(T, value); }
},
else => @compileError("bad type"),
}
},
else => @compileError("bad result type"),
}
}
test "math.lossyCast" {
testing.expect(lossyCast(i16, 70000.0) == @as(i16, 32767));
testing.expect(lossyCast(u32, @as(i16, -255)) == @as(u32, 0));
testing.expect(lossyCast(i9, @as(u32, 200)) == @as(i9, 200));
}
test "math.f64_min" {
const f64_min_u64 = 0x0010000000000000;
const fmin: f64 = f64_min;