Merge pull request #6189 from katesuyu/div-ceil

std: Add std.math.divCeil

Author: andrewrk

lib/std/math.zig

@@ -596,6 +596,59 @@ fn testDivFloor() void {
     testing.expect((divFloor(f32, -5.0, 3.0) catch unreachable) == -2.0);
 }
 
+pub fn divCeil(comptime T: type, numerator: T, denominator: T) !T {
+    @setRuntimeSafety(false);
+    if (comptime std.meta.trait.isNumber(T) and denominator == 0) return error.DivisionByZero;
+    const info = @typeInfo(T);
+    switch (info) {
+        .ComptimeFloat, .Float => return @ceil(numerator / denominator),
+        .ComptimeInt, .Int => {
+            if (numerator < 0 and denominator < 0) {
+                if (info == .Int and numerator == minInt(T) and denominator == -1)
+                    return error.Overflow;
+                return @divFloor(numerator + 1, denominator) + 1;
+            }
+            if (numerator > 0 and denominator > 0)
+                return @divFloor(numerator - 1, denominator) + 1;
+            return @divTrunc(numerator, denominator);
+        },
+        else => @compileError("divCeil unsupported on " ++ @typeName(T)),
+    }
+}
+
+test "math.divCeil" {
+    testDivCeil();
+    comptime testDivCeil();
+}
+fn testDivCeil() void {
+    testing.expectEqual(@as(i32, 2), divCeil(i32, 5, 3) catch unreachable);
+    testing.expectEqual(@as(i32, -1), divCeil(i32, -5, 3) catch unreachable);
+    testing.expectEqual(@as(i32, -1), divCeil(i32, 5, -3) catch unreachable);
+    testing.expectEqual(@as(i32, 2), divCeil(i32, -5, -3) catch unreachable);
+    testing.expectEqual(@as(i32, 0), divCeil(i32, 0, 5) catch unreachable);
+    testing.expectEqual(@as(u32, 0), divCeil(u32, 0, 5) catch unreachable);
+    testing.expectError(error.DivisionByZero, divCeil(i8, -5, 0));
+    testing.expectError(error.Overflow, divCeil(i8, -128, -1));
+
+    testing.expectEqual(@as(f32, 0.0), divCeil(f32, 0.0, 5.0) catch unreachable);
+    testing.expectEqual(@as(f32, 2.0), divCeil(f32, 5.0, 3.0) catch unreachable);
+    testing.expectEqual(@as(f32, -1.0), divCeil(f32, -5.0, 3.0) catch unreachable);
+    testing.expectEqual(@as(f32, -1.0), divCeil(f32, 5.0, -3.0) catch unreachable);
+    testing.expectEqual(@as(f32, 2.0), divCeil(f32, -5.0, -3.0) catch unreachable);
+
+    testing.expectEqual(6, divCeil(comptime_int, 23, 4) catch unreachable);
+    testing.expectEqual(-5, divCeil(comptime_int, -23, 4) catch unreachable);
+    testing.expectEqual(-5, divCeil(comptime_int, 23, -4) catch unreachable);
+    testing.expectEqual(6, divCeil(comptime_int, -23, -4) catch unreachable);
+    testing.expectError(error.DivisionByZero, divCeil(comptime_int, 23, 0));
+
+    testing.expectEqual(6.0, divCeil(comptime_float, 23.0, 4.0) catch unreachable);
+    testing.expectEqual(-5.0, divCeil(comptime_float, -23.0, 4.0) catch unreachable);
+    testing.expectEqual(-5.0, divCeil(comptime_float, 23.0, -4.0) catch unreachable);
+    testing.expectEqual(6.0, divCeil(comptime_float, -23.0, -4.0) catch unreachable);
+    testing.expectError(error.DivisionByZero, divCeil(comptime_float, 23.0, 0.0));
+}
+
 pub fn divExact(comptime T: type, numerator: T, denominator: T) !T {
     @setRuntimeSafety(false);
     if (denominator == 0) return error.DivisionByZero;