# Ticket #8398 (closed Bugs: fixed)

## dijkstra_shortest_paths implicitly requires DistanceMap and WeightMap to be the same

Reported by: | Luis G. Torres <lgtorres42@…> | Owned by: | jewillco |
---|---|---|---|

Milestone: | To Be Determined | Component: | graph |

Version: | Boost 1.53.0 | Severity: | Problem |

Keywords: | BGL, dijkstra | Cc: |

### Description

The documentation for dijkstra_shortest_paths states that the given distance_compare functor needs to be a BinaryPredicate? where both arguments are of the value type of DistanceMap?. The distance_combine functor needs to be a BinaryFunction? where the first argument is of the DistanceMap? value type and the second argument is of the WeightMap? value type.

However, in line 162 of dijkstra_shortest_paths.hpp, a comparison is made between a value from WeightMap? and a value from DistanceMap? using the distance_compare functor; this violates where the documentation specifies that the distance_compare functor would only need to handle types from DistanceMap?. Effectively, this requires either:

a) the value types of WeightMap? and DistanceMap? are made the same b) the distance_compare functor overloads operator() to have two different types of comparison

I imagine that fixing this issue would require either changing the documentation or changing line 162 to not require this comparison to be made (it seems to only be a way of verifying that there are no negative edges in the graph).

## Attachments

## Change History

**Note:**See TracTickets for help on using tickets.

(In [83772]) Changed test for negative edges per #8398; fixes #8398