From 43f90b21592f5ab4885d63a351e7caa3b5bdb225 Mon Sep 17 00:00:00 2001
From: frozolotl <44589151+frozolotl@users.noreply.github.com>
Date: Fri, 17 Nov 2023 19:55:57 +0100
Subject: [PATCH] Implement euclidean division and remainder (#2678)

---
 crates/typst-library/src/compute/calc.rs | 58 +++++++++++++++++++++++-
 tests/typ/compute/calc.typ               | 32 +++++++++++++
 2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/crates/typst-library/src/compute/calc.rs b/crates/typst-library/src/compute/calc.rs
index 83bf924ed..6276905c5 100644
--- a/crates/typst-library/src/compute/calc.rs
+++ b/crates/typst-library/src/compute/calc.rs
@@ -50,6 +50,8 @@ fn module() -> Module {
     scope.define_func::<even>();
     scope.define_func::<odd>();
     scope.define_func::<rem>();
+    scope.define_func::<div_euclid>();
+    scope.define_func::<rem_euclid>();
     scope.define_func::<quo>();
     scope.define("inf", f64::INFINITY);
     scope.define("nan", f64::NAN);
@@ -790,7 +792,10 @@ pub fn odd(
 /// in magnitude than `y`.
 ///
 /// ```example
-/// #calc.rem(20, 6) \
+/// #calc.rem(7, 3) \
+/// #calc.rem(7, -3) \
+/// #calc.rem(-7, 3) \
+/// #calc.rem(-7, -3) \
 /// #calc.rem(1.75, 0.5)
 /// ```
 #[func(title = "Remainder")]
@@ -806,6 +811,57 @@ pub fn rem(
     Ok(dividend.apply2(divisor.v, Rem::rem, Rem::rem))
 }
 
+/// Performs euclidean division of two numbers.
+///
+/// The result of this computation is that of a division rounded to the integer
+/// `{n}` such that the dividend is greater than or equal to `{n}` times the divisor.
+///
+/// ```example
+/// #calc.div-euclid(7, 3) \
+/// #calc.div-euclid(7, -3) \
+/// #calc.div-euclid(-7, 3) \
+/// #calc.div-euclid(-7, -3) \
+/// #calc.div-euclid(1.75, 0.5)
+/// ```
+#[func(title = "Euclidean Division")]
+pub fn div_euclid(
+    /// The dividend of the division.
+    dividend: Num,
+    /// The divisor of the division.
+    divisor: Spanned<Num>,
+) -> SourceResult<Num> {
+    if divisor.v.float() == 0.0 {
+        bail!(divisor.span, "divisor must not be zero");
+    }
+    Ok(dividend.apply2(divisor.v, i64::div_euclid, f64::div_euclid))
+}
+
+/// This calculates the least nonnegative remainder of a division.
+///
+/// Warning: Due to a floating point round-off error, the remainder may equal the absolute
+/// value of the divisor if the dividend is much smaller in magnitude than the divisor
+/// and the dividend is negative. This only applies for floating point inputs.
+///
+/// ```example
+/// #calc.rem-euclid(7, 3) \
+/// #calc.rem-euclid(7, -3) \
+/// #calc.rem-euclid(-7, 3) \
+/// #calc.rem-euclid(-7, -3) \
+/// #calc.rem(1.75, 0.5)
+/// ```
+#[func(title = "Euclidean Remainder")]
+pub fn rem_euclid(
+    /// The dividend of the remainder.
+    dividend: Num,
+    /// The divisor of the remainder.
+    divisor: Spanned<Num>,
+) -> SourceResult<Num> {
+    if divisor.v.float() == 0.0 {
+        bail!(divisor.span, "divisor must not be zero");
+    }
+    Ok(dividend.apply2(divisor.v, i64::rem_euclid, f64::rem_euclid))
+}
+
 /// Calculates the quotient (floored division) of two numbers.
 ///
 /// ```example
diff --git a/tests/typ/compute/calc.typ b/tests/typ/compute/calc.typ
index 24411ecfa..86dcafcdb 100644
--- a/tests/typ/compute/calc.typ
+++ b/tests/typ/compute/calc.typ
@@ -76,6 +76,38 @@
 // Error: 16-19 divisor must not be zero
 #calc.rem(3.0, 0.0)
 
+---
+// Test the `div-euclid` function.
+#test(calc.div-euclid(7, 3), 2)
+#test(calc.div-euclid(7, -3), -2)
+#test(calc.div-euclid(-7, 3), -3)
+#test(calc.div-euclid(-7, -3), 3)
+#test(calc.div-euclid(2.5, 2), 1)
+
+---
+// Error: 21-22 divisor must not be zero
+#calc.div-euclid(5, 0)
+
+---
+// Error: 23-26 divisor must not be zero
+#calc.div-euclid(3.0, 0.0)
+
+---
+// Test the `rem-euclid` function.
+#test(calc.rem-euclid(7, 3), 1)
+#test(calc.rem-euclid(7, -3), 1)
+#test(calc.rem-euclid(-7, 3), 2)
+#test(calc.rem-euclid(-7, -3), 2)
+#test(calc.rem-euclid(2.5, 2), 0.5)
+
+---
+// Error: 21-22 divisor must not be zero
+#calc.rem-euclid(5, 0)
+
+---
+// Error: 23-26 divisor must not be zero
+#calc.rem-euclid(3.0, 0.0)
+
 ---
 // Test the `quo` function.
 #test(calc.quo(1, 1), 1)