nalgebra/src/core/constraint.rs

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//! Compatibility constraints between matrix shapes, e.g., for addition or multiplication.
use core::dimension::{Dim, DimName, Dynamic};
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/// A type used in `where` clauses for enforcing constraints.
pub struct ShapeConstraint;
/// Constraints `C1` and `R2` to be equivalent.
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pub trait AreMultipliable<R1: Dim, C1: Dim, R2: Dim, C2: Dim>: DimEq<C1, R2> {}
impl<R1: Dim, C1: Dim, R2: Dim, C2: Dim> AreMultipliable<R1, C1, R2, C2> for ShapeConstraint
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where
ShapeConstraint: DimEq<C1, R2>,
{
}
/// Constraints `D1` and `D2` to be equivalent.
pub trait DimEq<D1: Dim, D2: Dim> {
/// This is either equal to `D1` or `D2`, always choosing the one (if any) which is a type-level
/// constant.
type Representative: Dim;
}
impl<D: Dim> DimEq<D, D> for ShapeConstraint {
type Representative = D;
}
impl<D: DimName> DimEq<D, Dynamic> for ShapeConstraint {
type Representative = D;
}
impl<D: DimName> DimEq<Dynamic, D> for ShapeConstraint {
type Representative = D;
}
macro_rules! equality_trait_decl(
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($($doc: expr, $Trait: ident),* $(,)*) => {$(
// XXX: we can't do something like `DimEq<D1> for D2` because we would require a blancket impl…
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#[doc = $doc]
pub trait $Trait<D1: Dim, D2: Dim>: DimEq<D1, D2> + DimEq<D2, D1> {
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/// This is either equal to `D1` or `D2`, always choosing the one (if any) which is a type-level
/// constant.
type Representative: Dim;
}
impl<D: Dim> $Trait<D, D> for ShapeConstraint {
type Representative = D;
}
impl<D: DimName> $Trait<D, Dynamic> for ShapeConstraint {
type Representative = D;
}
impl<D: DimName> $Trait<Dynamic, D> for ShapeConstraint {
type Representative = D;
}
)*}
);
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equality_trait_decl!(
"Constraints `D1` and `D2` to be equivalent. \
They are both assumed to be the number of \
rows of a matrix.",
SameNumberOfRows,
"Constraints `D1` and `D2` to be equivalent. \
They are both assumed to be the number of \
columns of a matrix.",
SameNumberOfColumns
);
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/// Constraints D1 and D2 to be equivalent, where they both designate dimensions of algebraic
/// entities (e.g. square matrices).
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pub trait SameDimension<D1: Dim, D2: Dim>
: SameNumberOfRows<D1, D2> + SameNumberOfColumns<D1, D2> {
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/// This is either equal to `D1` or `D2`, always choosing the one (if any) which is a type-level
/// constant.
type Representative: Dim;
}
impl<D: Dim> SameDimension<D, D> for ShapeConstraint {
type Representative = D;
}
impl<D: DimName> SameDimension<D, Dynamic> for ShapeConstraint {
type Representative = D;
}
impl<D: DimName> SameDimension<Dynamic, D> for ShapeConstraint {
type Representative = D;
}