Added dynamic version of neg.

src/compute/arithmetics/mod.rs

@@ -17,7 +17,7 @@ pub mod decimal;
 pub mod time;
 
 use crate::{
-    array::{Array, PrimitiveArray},
+    array::{Array, DictionaryArray, PrimitiveArray},
     bitmap::Bitmap,
     datatypes::{DataType, IntervalUnit, TimeUnit},
     scalar::{PrimitiveScalar, Scalar},
@@ -400,6 +400,72 @@ pub fn can_rem(lhs: &DataType, rhs: &DataType) -> bool {
     )
 }
 
+macro_rules! with_match_negatable {(
+    $key_type:expr, | $_:tt $T:ident | $($body:tt)*
+) => ({
+    macro_rules! __with_ty__ {( $_ $T:ident ) => ( $($body)* )}
+    use crate::datatypes::PrimitiveType::*;
+    use crate::types::{days_ms, months_days_ns};
+    match $key_type {
+        Int8 => __with_ty__! { i8 },
+        Int16 => __with_ty__! { i16 },
+        Int32 => __with_ty__! { i32 },
+        Int64 => __with_ty__! { i64 },
+        Int128 => __with_ty__! { i128 },
+        DaysMs => __with_ty__! { days_ms },
+        MonthDayNano => __with_ty__! { months_days_ns },
+        UInt8 | UInt16 | UInt32 | UInt64=> todo!(),
+        Float32 => __with_ty__! { f32 },
+        Float64 => __with_ty__! { f64 },
+    }
+})}
+
+/// Negates an [`Array`].
+/// # Panic
+/// This function panics iff either
+/// * the opertion is not supported for the logical type (use [`can_neg`] to check)
+/// * the operation overflows
+pub fn neg(array: &dyn Array) -> Box<dyn Array> {
+    use crate::datatypes::PhysicalType::*;
+    match array.data_type().to_physical_type() {
+        Primitive(primitive) => with_match_negatable!(primitive, |$T| {
+            let array = array.as_any().downcast_ref().unwrap();
+
+            let result = basic::negate::<$T>(array);
+            Box::new(result) as Box<dyn Array>
+        }),
+        Dictionary(key) => match_integer_type!(key, |$T| {
+            let array = array.as_any().downcast_ref::<DictionaryArray<$T>>().unwrap();
+
+            let values = neg(array.values().as_ref()).into();
+
+            Box::new(DictionaryArray::<$T>::from_data(array.keys().clone(), values)) as Box<dyn Array>
+        }),
+        _ => todo!(),
+    }
+}
+
+/// Whether [`neg`] is supported for a given [`DataType`]
+pub fn can_neg(data_type: &DataType) -> bool {
+    if let DataType::Dictionary(_, values) = data_type.to_logical_type() {
+        return can_neg(values.as_ref());
+    }
+
+    use crate::datatypes::PhysicalType::*;
+    use crate::datatypes::PrimitiveType::*;
+    matches!(
+        data_type.to_physical_type(),
+        Primitive(Int8)
+            | Primitive(Int16)
+            | Primitive(Int32)
+            | Primitive(Int64)
+            | Primitive(Float64)
+            | Primitive(Float32)
+            | Primitive(DaysMs)
+            | Primitive(MonthDayNano)
+    )
+}
+
 /// Defines basic addition operation for primitive arrays
 pub trait ArrayAdd<Rhs>: Sized {
     /// Adds itself to `rhs`

src/types/mod.rs

@@ -7,7 +7,7 @@
 //! represent chunks of bits (e.g. `u8`, `u16`), and [`BitChunkIter`], that can be used to
 //! iterate over bitmaps in [`BitChunk`]s.
 //! Finally, this module also contains traits used to compile code optimized for SIMD instructions at [`mod@simd`].
-use std::convert::TryFrom;
+use std::{convert::TryFrom, ops::Neg};
 
 mod bit_chunk;
 pub use bit_chunk::{BitChunk, BitChunkIter};
@@ -399,3 +399,21 @@ impl months_days_ns {
         self.2
     }
 }
+
+impl Neg for days_ms {
+    type Output = Self;
+
+    #[inline(always)]
+    fn neg(self) -> Self::Output {
+        Self([-self.0[0], -self.0[0]])
+    }
+}
+
+impl Neg for months_days_ns {
+    type Output = Self;
+
+    #[inline(always)]
+    fn neg(self) -> Self::Output {
+        Self(-self.0, -self.1, -self.2)
+    }
+}

tests/it/compute/arithmetics/mod.rs

@@ -2,7 +2,7 @@ mod basic;
 mod decimal;
 mod time;
 
-use arrow2::array::{new_empty_array, Int32Array};
+use arrow2::array::*;
 use arrow2::compute::arithmetics::*;
 use arrow2::datatypes::DataType::*;
 use arrow2::datatypes::{IntervalUnit, TimeUnit};
@@ -84,3 +84,25 @@ fn consistency() {
         }
     });
 }
+
+#[test]
+fn test_neg() {
+    let a = Int32Array::from(&[None, Some(6), None, Some(6)]);
+    let result = neg(&a);
+    let expected = Int32Array::from(&[None, Some(-6), None, Some(-6)]);
+    assert_eq!(expected, result.as_ref());
+}
+
+#[test]
+fn test_neg_dict() {
+    let a = DictionaryArray::<u8>::from_data(
+        UInt8Array::from_slice(&[0, 0, 1]),
+        std::sync::Arc::new(Int8Array::from_slice(&[1, 2])),
+    );
+    let result = neg(&a);
+    let expected = DictionaryArray::<u8>::from_data(
+        UInt8Array::from_slice(&[0, 0, 1]),
+        std::sync::Arc::new(Int8Array::from_slice(&[-1, -2])),
+    );
+    assert_eq!(expected, result.as_ref());
+}