Function exponential_sum_connectivity 

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

Compute the exponential sum-connectivity index.

eSC(G) = Σ_{(u,v)∈E} e^{1/√(d(u)+d(v))}

Self-loops are skipped. Returns 0.0 for edgeless graphs.

Examples

use rust_igraph::{Graph, exponential_sum_connectivity};

// K_3: 3 edges, each d=(2,2) → 3·e^{1/2}
let g = Graph::from_edges(&[(0,1),(1,2),(0,2)], false, Some(3)).unwrap();
assert!((exponential_sum_connectivity(&g).unwrap() - 3.0 * 0.5_f64.exp()).abs() < 1e-10);