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const std = @import("../std.zig");
const math = std.math;
const testing = std.testing;
/// Returns the natural logarithm of x.
///
/// Special Cases:
/// - ln(+inf) = +inf
/// - ln(0) = -inf
/// - ln(x) = nan if x < 0
/// - ln(nan) = nan
/// TODO remove this in favor of `@log`.
pub fn ln(x: anytype) @TypeOf(x) {
const T = @TypeOf(x);
switch (@typeInfo(T)) {
.ComptimeFloat => {
return @as(comptime_float, @log(x));
},
.Float => return @log(x),
.ComptimeInt => {
return @as(comptime_int, @floor(@log(@as(f64, x))));
},
.Int => |IntType| switch (IntType.signedness) {
.signed => @compileError("ln not implemented for signed integers"),
.unsigned => return @as(T, @floor(@log(@as(f64, x)))),
},
else => @compileError("ln not implemented for " ++ @typeName(T)),
}
}
test "math.ln" {
try testing.expect(ln(@as(f32, 0.2)) == @log(0.2));
try testing.expect(ln(@as(f64, 0.2)) == @log(0.2));
}
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