Function edge_degree_diff_ratio 

pub fn edge_degree_diff_ratio(graph: &Graph) -> IgraphResult<f64>

Compute the degree difference ratio over edges.

Σ_{(u,v)∈E} |d(u) - d(v)| / (d(u) + d(v))

Each edge contributes a value in [0, 1). Returns 0.0 for regular or edgeless graphs. Self-loops and zero-degree endpoints are skipped.

Examples

use rust_igraph::{Graph, edge_degree_diff_ratio};

// K_3: all (2,2) → |0|/4 = 0 per edge → 0.0
let g = Graph::from_edges(&[(0,1),(1,2),(0,2)], false, Some(3)).unwrap();
assert!(edge_degree_diff_ratio(&g).unwrap().abs() < 1e-10);