geometric-traits 0.2.3

Trait-based algebraic and graph algorithms for Rust, supporting no_std environments
Documentation 
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//! Submodule for the transposed graph traits.

use num_traits::Zero;

use super::Edges;
use crate::traits::{
    BiMatrix2D, SizedRowsSparseMatrix2D, SizedSparseBiMatrix2D, SparseBiMatrix2D, SparseMatrix2D,
};

/// Trait defining the properties of a transposed graph.
pub trait TransposedEdges: Edges<Matrix = <Self as TransposedEdges>::BiMatrix> {
    /// The type of matrix required to store the transposed edges.
    type BiMatrix: SizedSparseBiMatrix2D<RowIndex = Self::SourceNodeId, ColumnIndex = Self::DestinationNodeId>;

    /// Returns the predecessors of the node with the given identifier.
    ///
    /// # Arguments
    ///
    /// * `destination_node_id` - The identifier of the destination node.
    #[inline]
    fn predecessors(
        &self,
        destination_node_id: Self::DestinationNodeId,
    ) -> <<Self::BiMatrix as SparseBiMatrix2D>::SparseTransposedMatrix as SparseMatrix2D>::SparseRow<'_>
{
        self.matrix().sparse_column(destination_node_id)
    }

    /// Returns whether the given destination has that predecessor.
    ///
    /// # Arguments
    ///
    /// * `destination_node_id` - The identifier of the destination node.
    /// * `source_node_id` - The identifier of the source node.
    #[inline]
    fn has_predecessor(
        &self,
        destination_node_id: Self::DestinationNodeId,
        source_node_id: Self::SourceNodeId,
    ) -> bool {
        self.matrix().transposed().has_entry(destination_node_id, source_node_id)
    }

    /// Returns whether the given destination has any predecessor.
    ///
    /// # Arguments
    ///
    /// * `destination_node_id` - The identifier of the destination node.
    #[inline]
    fn has_predecessors(&self, destination_node_id: Self::DestinationNodeId) -> bool {
        self.in_degree(destination_node_id) > Self::SourceNodeId::zero()
    }

    /// Returns the inbound degree of the node with the given identifier.
    ///
    /// # Arguments
    ///
    /// * `destination_node_id` - The identifier of the destination node.
    #[inline]
    fn in_degree(&self, destination_node_id: Self::DestinationNodeId) -> Self::SourceNodeId {
        self.matrix().number_of_defined_values_in_column(destination_node_id)
    }

    /// Returns an iterator over the in-bound degrees of the nodes.
    #[inline]
    fn in_degrees(&self) -> <<Self::BiMatrix as SparseBiMatrix2D>::SparseTransposedMatrix as SizedRowsSparseMatrix2D>::SparseRowSizes<'_>{
        self.matrix().sparse_column_sizes()
    }
}

impl<E: Edges> TransposedEdges for E
where
    E::Matrix:
        SizedSparseBiMatrix2D<RowIndex = E::SourceNodeId, ColumnIndex = E::DestinationNodeId>,
{
    type BiMatrix = E::Matrix;
}