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Document NumCast / ToPrimitive's sucess vs error rules #137

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merged 3 commits into from
Nov 12, 2019
Merged

Document NumCast / ToPrimitive's sucess vs error rules #137

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16cdce3
FromPrimitive: fix some comments
ocstl Oct 18, 2019
27e3f85
NumCast: document when `from` can return `None`
ocstl Oct 18, 2019
fdb4181
ToPrimitive: document when `to_` methods can return `None`
ocstl Oct 18, 2019
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109 changes: 63 additions & 46 deletions src/cast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,74 +10,88 @@ use float::FloatCore;

/// A generic trait for converting a value to a number.
pub trait ToPrimitive {
/// Converts the value of `self` to an `isize`.
/// Converts the value of `self` to an `isize`. If the value cannot be
/// represented by an `isize`, then `None` is returned.
#[inline]
fn to_isize(&self) -> Option<isize> {
self.to_i64().as_ref().and_then(ToPrimitive::to_isize)
}

/// Converts the value of `self` to an `i8`.
/// Converts the value of `self` to an `i8`. If the value cannot be
/// represented by an `i8`, then `None` is returned.
#[inline]
fn to_i8(&self) -> Option<i8> {
self.to_i64().as_ref().and_then(ToPrimitive::to_i8)
}

/// Converts the value of `self` to an `i16`.
/// Converts the value of `self` to an `i16`. If the value cannot be
/// represented by an `i16`, then `None` is returned.
#[inline]
fn to_i16(&self) -> Option<i16> {
self.to_i64().as_ref().and_then(ToPrimitive::to_i16)
}

/// Converts the value of `self` to an `i32`.
/// Converts the value of `self` to an `i32`. If the value cannot be
/// represented by an `i32`, then `None` is returned.
#[inline]
fn to_i32(&self) -> Option<i32> {
self.to_i64().as_ref().and_then(ToPrimitive::to_i32)
}

/// Converts the value of `self` to an `i64`.
/// Converts the value of `self` to an `i64`. If the value cannot be
/// represented by an `i64`, then `None` is returned.
fn to_i64(&self) -> Option<i64>;

/// Converts the value of `self` to an `i128`.
/// Converts the value of `self` to an `i128`. If the value cannot be
/// represented by an `i128` (`i64` under the default implementation), then
/// `None` is returned.
///
/// This method is only available with feature `i128` enabled on Rust >= 1.26.
///
/// The default implementation converts through `to_i64()`. Types implementing
/// The default implementation converts through `to_i64()`. Types implementing
/// this trait should override this method if they can represent a greater range.
#[inline]
#[cfg(has_i128)]
fn to_i128(&self) -> Option<i128> {
self.to_i64().map(From::from)
}

/// Converts the value of `self` to a `usize`.
/// Converts the value of `self` to a `usize`. If the value cannot be
/// represented by a `usize`, then `None` is returned.
#[inline]
fn to_usize(&self) -> Option<usize> {
self.to_u64().as_ref().and_then(ToPrimitive::to_usize)
}

/// Converts the value of `self` to an `u8`.
/// Converts the value of `self` to a `u8`. If the value cannot be
/// represented by a `u8`, then `None` is returned.
#[inline]
fn to_u8(&self) -> Option<u8> {
self.to_u64().as_ref().and_then(ToPrimitive::to_u8)
}

/// Converts the value of `self` to an `u16`.
/// Converts the value of `self` to a `u16`. If the value cannot be
/// represented by a `u16`, then `None` is returned.
#[inline]
fn to_u16(&self) -> Option<u16> {
self.to_u64().as_ref().and_then(ToPrimitive::to_u16)
}

/// Converts the value of `self` to an `u32`.
/// Converts the value of `self` to a `u32`. If the value cannot be
/// represented by a `u32`, then `None` is returned.
#[inline]
fn to_u32(&self) -> Option<u32> {
self.to_u64().as_ref().and_then(ToPrimitive::to_u32)
}

/// Converts the value of `self` to an `u64`.
/// Converts the value of `self` to a `u64`. If the value cannot be
/// represented by a `u64`, then `None` is returned.
#[inline]
fn to_u64(&self) -> Option<u64>;

/// Converts the value of `self` to an `u128`.
/// Converts the value of `self` to a `u128`. If the value cannot be
/// represented by a `u128` (`u64` under the default implementation), then
/// `None` is returned.
///
/// This method is only available with feature `i128` enabled on Rust >= 1.26.
///
Expand All @@ -89,13 +103,15 @@ pub trait ToPrimitive {
self.to_u64().map(From::from)
}

/// Converts the value of `self` to an `f32`.
/// Converts the value of `self` to an `f32`. If the value cannot be
/// represented by an `f32`, then `None` is returned.
#[inline]
fn to_f32(&self) -> Option<f32> {
self.to_f64().as_ref().and_then(ToPrimitive::to_f32)
}

/// Converts the value of `self` to an `f64`.
/// Converts the value of `self` to an `f64`. If the value cannot be
/// represented by an `f64`, then `None` is returned.
#[inline]
fn to_f64(&self) -> Option<f64> {
match self.to_i64() {
Expand Down Expand Up @@ -362,105 +378,105 @@ impl_to_primitive_float!(f64);

/// A generic trait for converting a number to a value.
pub trait FromPrimitive: Sized {
/// Convert an `isize` to return an optional value of this type. If the
/// value cannot be represented by this value, then `None` is returned.
/// Converts an `isize` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_isize(n: isize) -> Option<Self> {
n.to_i64().and_then(FromPrimitive::from_i64)
}

/// Convert an `i8` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `i8` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_i8(n: i8) -> Option<Self> {
FromPrimitive::from_i64(From::from(n))
}

/// Convert an `i16` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `i16` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_i16(n: i16) -> Option<Self> {
FromPrimitive::from_i64(From::from(n))
}

/// Convert an `i32` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `i32` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_i32(n: i32) -> Option<Self> {
FromPrimitive::from_i64(From::from(n))
}

/// Convert an `i64` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `i64` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
fn from_i64(n: i64) -> Option<Self>;

/// Convert an `i128` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `i128` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
///
/// This method is only available with feature `i128` enabled on Rust >= 1.26.
///
/// The default implementation converts through `from_i64()`. Types implementing
/// The default implementation converts through `from_i64()`. Types implementing
/// this trait should override this method if they can represent a greater range.
#[inline]
#[cfg(has_i128)]
fn from_i128(n: i128) -> Option<Self> {
n.to_i64().and_then(FromPrimitive::from_i64)
}

/// Convert a `usize` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts a `usize` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_usize(n: usize) -> Option<Self> {
n.to_u64().and_then(FromPrimitive::from_u64)
}

/// Convert an `u8` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `u8` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_u8(n: u8) -> Option<Self> {
FromPrimitive::from_u64(From::from(n))
}

/// Convert an `u16` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `u16` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_u16(n: u16) -> Option<Self> {
FromPrimitive::from_u64(From::from(n))
}

/// Convert an `u32` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `u32` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_u32(n: u32) -> Option<Self> {
FromPrimitive::from_u64(From::from(n))
}

/// Convert an `u64` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `u64` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
fn from_u64(n: u64) -> Option<Self>;

/// Convert an `u128` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts an `u128` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
///
/// This method is only available with feature `i128` enabled on Rust >= 1.26.
///
/// The default implementation converts through `from_u64()`. Types implementing
/// The default implementation converts through `from_u64()`. Types implementing
/// this trait should override this method if they can represent a greater range.
#[inline]
#[cfg(has_i128)]
fn from_u128(n: u128) -> Option<Self> {
n.to_u64().and_then(FromPrimitive::from_u64)
}

/// Convert a `f32` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts a `f32` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_f32(n: f32) -> Option<Self> {
FromPrimitive::from_f64(From::from(n))
}

/// Convert a `f64` to return an optional value of this type. If the
/// type cannot be represented by this value, then `None` is returned.
/// Converts a `f64` to return an optional value of this type. If the
/// value cannot be represented by this type, then `None` is returned.
#[inline]
fn from_f64(n: f64) -> Option<Self> {
match n.to_i64() {
Expand Down Expand Up @@ -639,7 +655,8 @@ pub fn cast<T: NumCast, U: NumCast>(n: T) -> Option<U> {
/// An interface for casting between machine scalars.
pub trait NumCast: Sized + ToPrimitive {
/// Creates a number from another value that can be converted into
/// a primitive via the `ToPrimitive` trait.
/// a primitive via the `ToPrimitive` trait. If the source value cannot be
/// represented by the target type, then `None` is returned.
fn from<T: ToPrimitive>(n: T) -> Option<Self>;
}

Expand Down