[ library(graph_algorithms) | Reference Manual | Alphabetic Index ]

# make_graph(+NNodes, ++EdgeList, -Graph)

Creates a graph with minimal overhead
NNodes
the number of nodes: integer >= 0
EdgeList
a (possibly empty) list of e/3 structures in no particular order
Graph
will be bound to a graph structure

## Description

This predicate creates a graph data structure according to the given information. A graph consists of nodes that are numbered from 1 to NNodes and directed edges between the nodes. An edge is represented by the data structure

```	e(Source, Target, EdgeData)
```
where Source and Target are integers indicating the start and end point of the edge, and EdgeData is an arbitrary data structure holding additional information about the edge, e.g. capacity, distance, weight, name etc. The EdgeData field should have the same structure for all edges in the graph. If there is no information attached to edges, the field should be set to 1 for edges between different nodes and to 0 otherwise. Several library predicates inspect the EdgeData field or an argument of the EdgeData field, e.g. the shortest path predicate can use any numeric component of EdgeData as the distance criterion. Caution: the distance arguments will be compared using general term comparison (see compare/3) and should therefore have the same type in all edges (e.g. all integer or all float).

### Modes and Determinism

• make_graph(+, ++, -) is det

### Fail Conditions

Edges contain nonexisting node numbers

### Exceptions

(6) out of range
NNodes is negative
(4) instantiation fault
NNodes or EdgeList are uninstantiated
(5) type error
NNodes is not integral

## Examples

```    % the 13-node undirected graph from Sedgewick:Algorithms
make_graph( 13,
[ e(1,6,1),e(1,2,1),e(1,7,1),e(3,1,1),e(4,6,1),e(5,4,1),
e(6,5,1),e(7,5,1),e(7,10,1),e(7,3,1),e(8,7,1),e(8,9,1),e(9,8,1),
e(10,11,1),e(10,12,1),e(10,13,1),e(12,7,1),e(12,13,1),e(13,12,1) ],
Graph).```