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FriCAS currently has a subsystem forgraphs. The discussion below is morstly of historical interest. Note that some names in code below are the same as names in current implementation which causes conflicts and weird error messages...

We want an implementation of the mathematical concept of graphgraph* in the sense of Graph Theory See also: Graph_(mathematics) The concept of a graph is fundamental in many areas of mathematics and is the starting point for category theory. Graphs are also very important data structures in many algorithms in computer science. Our goal here therefore is to develop the concept of graph in FriCAS in the most general way possible.

Axiom Version

fricas
)version
Value = "FriCAS 1.3.7 compiled at Wed Jun 30 16:44:06 UTC 2021"

## Aldor Verison

First we define the general category of graphs. Note that we use a [lowercase] short name graphcat for GraphCategory?.

aldor
#include "axiom.as"
define GraphCategory(nodes:Type, edges:Type): Category == with {
source:edges->nodes;
target:edges->nodes;
}
aldor
Compiling FriCAS source code from file
/var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/graphcat.as
using Aldor compiler and options
-O -Fasy -Fao -Flsp -lfricas -Mno-ALDOR_W_WillObsolete -DFriCAS -Y $FRICAS/algebra -I$FRICAS/algebra
Use the system command )set compiler args to change these
options.
The )library system command was not called after compilation.

Now we define finite graphs as follows:

aldor
#include "axiom.as";
#library graphcat "graphcat.ao";
import from graphcat;
inline from graphcat;
edges ==> Record(source:nodes,target:nodes);
FiniteGraph(nodes: BasicType): GraphCategory(nodes,edges) with { new: %; addNode:(%,nodes)->nodes; addEdge:(%,nodes,nodes)-> edges; } == add { Rep == Record(node: List nodes, edge: List edges);
new:% == { n:List(nodes):=[]; e:List(edges):=[]; r:Rep:=[n,e]; per(r); }; addNode(g:%,n:nodes):nodes == { concat(rep(g).node,n); n; }; addEdge(g:%,n1:nodes,n2:nodes):edges == { concat(rep(g).edge,[n1,n2]); [n1,n2]; };
source(ed:edges):nodes == ed.source; target(ed:edges):nodes == ed.target; }
aldor
Compiling FriCAS source code from file
/var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/fgraph.as
using Aldor compiler and options
-O -Fasy -Fao -Flsp -lfricas -Mno-ALDOR_W_WillObsolete -DFriCAS -Y $FRICAS/algebra -I$FRICAS/algebra
Use the system command )set compiler args to change these
options.
The )library system command was not called after compilation.

Make sure that FiniteGraph? and GraphCategory? are known to FriCAS:

\begin{axiom}
)lisp (si::allocate-contiguous-pages 3000 t)
)library graphcat fgraph
\end{axiom}

If we use UPPERCASE in the name of the Aldor library the example below results in:

>> System error:
AxiomXL file "GRAPHCAT" is missing!

But if we use lowercase, it (sometimes) works! However quite often when we refresh this page even without editing it, we get now the error:

>> System error:
Contiguous blocks exhausted.
Currently, 1354 pages are allocated.
Use ALLOCATE-CONTIGUOUS-PAGES to expand the space.

Example 1: create a simple finite graph:

fricas
g:FiniteGraph(INT)
FiniteGraph(Integer) is a category, not a domain, and declarations require domains.

Why do I need to specify $FiniteGraph(INT) in this case but not in the next example? fricas source(e)$FiniteGraph(INT)
The right-hand side of the $operator must be a package or domain name, but FiniteGraph(Integer) is a category. But without the category definition this seems to be ok? aldor #include "axiom.as" edges ==> Record(source:nodes,target:nodes); FiniteGraph(nodes: BasicType): -- GraphCategory(nodes,edges) with { source:edges->nodes; target:edges->nodes; new: %; addNode:(%,nodes)->nodes; addEdge:(%,nodes,nodes)-> edges; } == add { Rep == Record(node: List nodes, edge: List edges); new:% == { n:List(nodes):=[]; e:List(edges):=[]; r:Rep:=[n,e]; per(r); }; addNode(g:%,n:nodes):nodes == { concat(rep(g).node,n); n; }; addEdge(g:%,n1:nodes,n2:nodes):edges == { concat(rep(g).edge,[n1,n2]); [n1,n2]; }; source(ed:edges):nodes == ed.source; target(ed:edges):nodes == ed.target; } aldor Compiling FriCAS source code from file /var/lib/zope2.10/instance/axiom-wiki/var/LatexWiki/8126689142996008028-25px006.as using Aldor compiler and options -O -Fasy -Fao -Flsp -lfricas -Mno-ALDOR_W_WillObsolete -DFriCAS -Y$FRICAS/algebra -I \$FRICAS/algebra
Use the system command )set compiler args to change these
options.
The )library system command was not called after compilation.

Example 2: create a simple finite graph:

fricas
g:FiniteGraph(INT)
FiniteGraph(Integer) is a category, not a domain, and declarations require domains.

fricas
)lisp (room)
Dynamic space usage is: 77,439,648 bytes. Read-only space usage is: 5,952 bytes. Static space usage is: 4,000 bytes. Control stack usage is: 3,504 bytes. Binding stack usage is: 736 bytes. Control and binding stack usage is for the current thread only. Garbage collection is currently enabled.
Breakdown for dynamic space: 20,995,888 bytes for 21,409 code objects. 19,215,632 bytes for 1,200,977 cons objects. 11,700,544 bytes for 107,358 simple-vector objects. 10,441,440 bytes for 119,663 instance objects. 4,393,792 bytes for 50,213 simple-character-string objects. 10,692,352 bytes for 189,166 other objects. 77,439,648 bytes for 1,688,786 dynamic objects (space total.) Value = NIL

Here is another Aldor version SandBox Category of Graphs 2

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