[GitHub] [arrow-rs] alamb commented on a change in pull request #414: Doctests for DecimalArray.

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #414:
URL: https://github.com/apache/arrow-rs/pull/414#discussion_r646115328



##########
File path: arrow/src/array/array_binary.rs
##########
@@ -613,6 +613,32 @@ impl Array for FixedSizeBinaryArray {
 }
 
 /// A type of `DecimalArray` whose elements are binaries.
+///
+/// # Examples
+///
+/// ```
+///    use arrow::array::{ArrayData, Array, DecimalArray};
+///    use arrow::buffer::Buffer;
+///    use arrow::datatypes::DataType;
+///    // let val_8887: [u8; 16] = [192, 219, 180, 17, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
+///    // let val_neg_8887: [u8; 16] = [64, 36, 75, 238, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255];
+///    let values: [u8; 32] = [
+///        192, 219, 180, 17, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 36, 75, 238, 253,
+///        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+///    ];
+///    let array_data = ArrayData::builder(DataType::Decimal(23, 6))
+///        .len(2)
+///        .add_buffer(Buffer::from(&values[..]))
+///        .build();
+///    let decimal_array = DecimalArray::from(array_data);
+///    assert_eq!(2, decimal_array.len());
+///    assert_eq!(8_887_000_000, decimal_array.value(0));
+///    assert_eq!(-8_887_000_000, decimal_array.value(1));
+///    assert_eq!(16, decimal_array.value_length());
+///    assert_eq!(23, decimal_array.precision());
+///    assert_eq!(6, decimal_array.scale());

Review comment:
       @alippai has an improvement for string formatting decimal values in https://github.com/apache/arrow-rs/pull/406
   
   If he adds the method to `DecimalArray` in https://github.com/apache/arrow-rs/pull/406#discussion_r646114701 it would be neat to also add it to the doc test. 

##########
File path: arrow/src/array/array_binary.rs
##########
@@ -613,6 +613,32 @@ impl Array for FixedSizeBinaryArray {
 }
 
 /// A type of `DecimalArray` whose elements are binaries.
+///
+/// # Examples
+///
+/// ```
+///    use arrow::array::{ArrayData, Array, DecimalArray};

Review comment:
       I think using the `DecimalBuilder` to construct a DecimalArray may make for a better example:
   
   For example, here:  https://github.com/apache/arrow-rs/blob/master/arrow/src/array/builder.rs#L2856




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