Introduce trunc_with_scale

paupino · Feb 28, 2023 · 8ae854a · 8ae854a
1 parent caee892
commit 8ae854a
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diff --git a/src/decimal.rs b/src/decimal.rs
@@ -805,6 +805,21 @@ impl Decimal {
         }
     }
 
+    /// Returns a new `Decimal` with the fractional portion delimited by `scale`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rust_decimal::Decimal;
+    /// #
+    /// let trunc = Decimal::from_parts(31415, 0, 0, false, 4);
+    /// assert_eq!(Decimal::PI.trunc_with_scale(4), trunc);
+    /// ```
+    #[must_use]
+    pub fn trunc_with_scale(&self, scale: u32) -> Decimal {
+        self.round_dp_with_strategy(scale, RoundingStrategy::ToZero)
+    }
+
     /// Returns a new `Decimal` representing the fractional portion of the number.
     ///
     /// # Example

diff --git a/tests/decimal_tests.rs b/tests/decimal_tests.rs
@@ -2485,6 +2485,29 @@ fn it_can_trunc() {
     }
 }
 
+#[test]
+fn it_can_trunc_with_scale() {
+    let cmp = Decimal::from_str("1.2345").unwrap();
+    assert_eq!(Decimal::from_str("1.23450").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("1.234500001").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("1.23451").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("1.23454").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("1.23455").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("1.23456").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("1.23459").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("1.234599999").unwrap().trunc_with_scale(4), cmp);
+
+    let cmp = Decimal::from_str("-1.2345").unwrap();
+    assert_eq!(Decimal::from_str("-1.23450").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("-1.234500001").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("-1.23451").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("-1.23454").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("-1.23455").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("-1.23456").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("-1.23459").unwrap().trunc_with_scale(4), cmp);
+    assert_eq!(Decimal::from_str("-1.234599999").unwrap().trunc_with_scale(4), cmp);
+}
+
 #[test]
 fn it_can_fract() {
     let tests = &[