docs/01-installation.markdown @ 884333cfb6fb v1.3.2

Detect *all* cycles during topological sort

Previously the cycle detection was limited to detecting when we hit
a currently-being-visited node during a traversal.  So something like this would
be correctly found:

    A --> B --> C
          ^     |
          |     |
          +-----+

We start at the root (A), go to B, then to C, then to B, and detect that we're
still working on B and signal the error.

But this doesn't find all cycles, because we *start* at the root nodes, and if
a cycle doesn't have any outcropping branches we'll never reach it at all.  For
example:

    A --> B
    ^     |
    |     |
    +-----+

This graph has no roots, so we incorrectly ignore the cycle.

This patch fixes the problem by keeping a count of visited nodes and and making
sure it matches the digraph's size at the end.

Fixes https://github.com/sjl/cl-digraph/issues/4

Installation
============

cl-digraph can be installed with [Quicklisp][]: `(ql:quickload :cl-digraph)`

The `cl-digraph` system contains the core API and has no dependencies.

The `cl-digraph.dot` system contains support for drawing digraphs with Graphviz
using [cl-dot][].

The `cl-digraph.test` system contains the test suite, which uses [1am][].

[quicklisp]: https://quicklisp.org/
[1am]: https://github.com/lmj/1am
[cl-dot]: https://github.com/michaelw/cl-dot