You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: type_conversion.rs
    path of file: ./repos/ndarray/examples
    
    the code of the file until where you have to start completion: #[cfg(feature = "approx")]
use std::convert::TryFrom;

#[cfg(feature = "approx")]
use approx::assert_abs_diff_eq;
#[cfg(feature = "approx")]
use ndarray::prelude::*;

#[cfg(feature = "approx")]
fn main() {
    // Converting an array from one datatype to another is implemented with the
    // `ArrayBase::mapv()` function. We pass a closure that is applied to each
    // element independently. This allows for more control and flexiblity in
    // converting types.
    //
    // Below, we illustrate four different approaches for the actual conversion
    // in the closure.
    // - `From` ensures lossless conversions known at compile time and is the
    //   best default choice.
    // - `TryFrom` either converts data losslessly or panics, ensuring that the
    //   rest of the program does not continue with unexpected data.
    // - `as` never panics and may silently convert in a lossy way, depending
    //   on the source and target datatypes. More details can be found in the
    //   reference: https://doc.rust-lang.org/reference/expressions/operator-expr.html#numeric-cast
    // - Using custom logic in the closure, e.g. to clip values or for NaN
    //   handling in floats.
    //
    // For a brush-up on casting between numeric types in Rust, refer to:
    // https://doc.rust-lang.org/rust-by-example/types/cast.html

    // Infallible, lossless conversion with `From`
    // The trait `std::convert::From` is only implemented for conversions that
    // can be guaranteed to be lossless at compile time. This is the safest
    // approach.
    let a_u8: Array<u8, _> = array![[1, 2, 3], [4, 5, 6]];
    let a_f32 = a_u8.mapv(|element| f32::from(element));
    assert_abs_diff_eq!(a_f32, array![[1.0, 2.0, 3.0], [4.0, 5.0, 6.0]]);

    // Fallible, lossless conversion with `TryFrom`
    // `i8` numbers can be negative, in such a case, there is no perfect
    // conversion to `u8` defined. In this example, all numbers are positive and
    // in bounds and can be converted at runtime. But for unknown runtime input,
    // this would panic with the message provided in `.expect()`. Note that you
    // can also use `.unwrap()` to be more concise.
    let a_i8: Array<i8, _> = array![120, 8, 0];
    let a_u8 = a_i8.mapv(|element| u8::try_from(element).expect("Could not convert i8 to u8"));
    assert_eq!(a_u8, array![120u8, 8u8, 0u8]);

    // Unsigned to signed integer conversion with `as`
    // A real-life example of this would be coordinates on a grid.
    // A `usize` value can be larger than what fits into a `isize`, therefore,
    // it would be safer to use `TryFrom`. Nevertheless, `as` can be used for
    // either simplicity or performance.
    // The example includes `usize::MAX` to illustrate potentially undesired
    // behavior. It will be interpreted as -1 (noop-casting + 2-complement), see
    // https://doc.rust-lang.org/reference/expressions/operator-expr.html#numeric-cast
    let a_usize: Array<usize, _> = array![1, 2, 3, usize::MAX];
    let a_isize = a_usize.mapv(|element| element as isize);
    assert_eq!(a_isize, array![1_isize, 2_isize, 3_isize, -1_isize]);

    // Simple upcasting with `as`
    // Every `u8` fits perfectly into a `u32`, therefore this is a lossless
    // conversion.
    // Note that it is up to the programmer to ensure the validity of the
    // conversion over the lifetime of a program. With type inference, subtle
    // bugs can creep in since conversions with `as` will always compile, so a
    // programmer might not notice that a prior lossless conversion became a
    // lossy conversion. With `From`, this would be noticed at compile-time and
    // with `TryFrom`, it would also be either handled or make the program
    // panic.
    let a_u8: Array<u8, _> = array![[1, 2, 3], [4, 5, 6]];
    let a_u32 = a_u8.mapv(|element| element as u32);
    assert_eq!(a_u32, array![[1u32, 2u32, 3u32], [4u32, 5u32, 6u32]]);

    // Saturating cast with `as`
    // The `as` keyword performs a *saturating cast* When casting floats to
    // ints. This means that numbers which do not fit into the target datatype
    // will silently be clipped to the maximum/minimum numbers. Since this is
    // not obvious, we discourage the intentional use of casting with `as` with
    // silent saturation and recommend a custom logic instead which makes the
    // intent clear.
    let a_f32: Array<f32, _> = array![
        256.0,         // saturated to 255
        255.7,         // saturated to 255
        255.1,         // saturated to 255
        254.7,         // rounded down to 254 by cutting the decimal part
        254.1,         // rounded down to 254 by cutting the decimal part
        -1.0,          // saturated to 0 on the lower end
        f32::INFINITY, // saturated to 255
        f32::NAN,      // converted to zero
    ];
    let a_u8 = a_f32.mapv(|element| element as u8);
    assert_eq!(a_u8, array![255, 255, 255, 254, 254, 0, 255, 0]);

    // Custom mapping logic
    // Given that we pass a closure for the conversion, we can also define
    // custom logic to e.g. replace NaN values and clip others. This also
    // makes the intent clear.
    let a_f32: Array<f32, _> = array![
        270.0,         // clipped to 200
        -1.2,          // 
    
fn main() {
    // Converting an array from one datatype to another is implemented with the
    // `ArrayBase::mapv()` function. We pass a closure that is applied to each
    // element independently. This allows for more control and flexiblity in
    // converting types.
    //
    // Below, we illustrate four different approaches for the actual conversion
    // in the closure.
    // - `From` ensures lossless conversions known at compile time and is the
    //   best default choice.
    // - `TryFrom` either converts data losslessly or panics, ensuring that the
    //   rest of the program does not continue with unexpected data.
    // - `as` never panics and may silently convert in a lossy way, depending
    //   on the source and target datatypes. More details can be found in the
    //   reference: https://doc.rust-lang.org/reference/expressions/operator-expr.html#numeric-cast
    // - Using custom logic in the closure, e.g. to clip values or for NaN
    //   handling in floats.
    //
    // For a brush-up on casting between numeric types in Rust, refer to:
    // https://doc.rust-lang.org/rust-by-example/types/cast.html

    // Infallible, lossless conversion with `From`
    // The trait `std::convert::From` is only implemented for conversions that
    // can be guaranteed to be lossless at compile time. This is the safest
    // approach.
    let a_u8: Array<u8, _> = array![[1, 2, 3], [4, 5, 6]];
    let a_f32 = a_u8.mapv(|element| f32::from(element));
    assert_abs_diff_eq!(a_f32, array![[1.0, 2.0, 3.0], [4.0, 5.0, 6.0]]);

    // Fallible, lossless conversion with `TryFrom`
    // `i8` numbers can be negative, in such a case, there is no perfect
    // conversion to `u8` defined. In this example, all numbers are positive and
    // in bounds and can be converted at runtime. But for unknown runtime input,
    // this would panic with the message provided in `.expect()`. Note that you
    // can also use `.unwrap()` to be more concise.
    let a_i8: Array<i8, _> = array![120, 8, 0];
    let a_u8 = a_i8.mapv(|element| u8::try_from(element).expect("Could not convert i8 to u8"));
    assert_eq!(a_u8, array![120u8, 8u8, 0u8]);

    // Unsigned to signed integer conversion with `as`
    // A real-life example of this would be coordinates on a grid.
    // A `usize` value can be larger than what fits into a `isize`, therefore,
    // it would be safer to use `TryFrom`. Nevertheless, `as` can be used for
    // either simplicity or performance.
    // The example includes `usize::MAX` to illustrate potentially undesired
    // behavior. It will be interpreted as -1 (noop-casting + 2-complement), see
    // https://doc.rust-lang.org/reference/expressions/operator-expr.html#numeric-cast
    let a_usize: Array<usize, _> = array![1, 2, 3, usize::MAX];
    let a_isize = a_usize.mapv(|element| element as isize);
    assert_eq!(a_isize, array![1_isize, 2_isize, 3_isize, -1_isize]);

    // Simple upcasting with `as`
    // Every `u8` fits perfectly into a `u32`, therefore this is a lossless
    // conversion.
    // Note that it is up to the programmer to ensure the validity of the
    // conversion over the lifetime of a program. With type inference, subtle
    // bugs can creep in since conversions with `as` will always compile, so a
    // programmer might not notice that a prior lossless conversion became a
    // lossy conversion. With `From`, this would be noticed at compile-time and
    // with `TryFrom`, it would also be either handled or make the program
    // panic.
    let a_u8: Array<u8, _> = array![[1, 2, 3], [4, 5, 6]];
    let a_u32 = a_u8.mapv(|element| element as u32);
    assert_eq!(a_u32, array![[1u32, 2u32, 3u32], [4u32, 5u32, 6u32]]);

    // Saturating cast with `as`
    // The `as` keyword performs a *saturating cast* When casting floats to
    // ints. This means that numbers which do not fit into the target datatype
    // will silently be clipped to the maximum/minimum numbers. Since this is
    // not obvious, we discourage the intentional use of casting with `as` with
    // silent saturation and recommend a custom logic instead which makes the
    // intent clear.
    let a_f32: Array<f32, _> = array![
        256.0,         // saturated to 255
        255.7,         // saturated to 255
        255.1,         // saturated to 255
        254.7,         // rounded down to 254 by cutting the decimal part
        254.1,         // rounded down to 254 by cutting the decimal part
        -1.0,          // saturated to 0 on the lower end
        f32::INFINITY, // saturated to 255
        f32::NAN,      // converted to zero
    ];
    let a_u8 = a_f32.mapv(|element| element as u8);
    assert_eq!(a_u8, array![255, 255, 255, 254, 254, 0, 255, 0]);

    // Custom mapping logic
    // Given that we pass a closure for the conversion, we can also define
    // custom logic to e.g. replace NaN values and clip others. This also
    // makes the intent clear.
    let a_f32: Array<f32, _> = array![
        270.0,         // clipped to 200
        -1.2,          // clipped to 0
        4.7,           // rounded up to 5 instead of just stripping decimals
        f32::INFINITY, // clipped to 200
        f32::NAN,      // replaced with upper bound 200
    ];
    let a_u8_custom = a_f32.mapv(|element| {
        if element == f32::INFINITY || element.is_nan() {
            return 200;
        }
        if let Some(std::cmp::Ordering::Less) = element.partial_cmp(&0.0) {
            return 0;
        }
        200.min(element.round() as u8)
    });
    assert_eq!(a_u8_custom, array![200, 0, 5, 200, 200]);
}