Add minimal WordGraph wrapper to unblock implementations

deps/src/CMakeLists.txt

@@ -50,6 +50,7 @@ add_library(libsemigroups_julia SHARED
     report.cpp
     runner.cpp
     transf.cpp
+    word-graph.cpp
     word-range.cpp
 )
 

deps/src/libsemigroups_julia.cpp

@@ -39,6 +39,7 @@ namespace libsemigroups_julia {
 
     define_order(mod);
     define_word_range(mod);
+    define_word_graph(mod);
   }
 
 }  // namespace libsemigroups_julia

deps/src/libsemigroups_julia.hpp

@@ -61,6 +61,7 @@ namespace libsemigroups_julia {
   void define_bmat8(jl::Module& mod);
   void define_order(jl::Module& mod);
   void define_word_range(jl::Module& mod);
+  void define_word_graph(jl::Module& mod);
 
 }  // namespace libsemigroups_julia
 

deps/src/word-graph.cpp

@@ -0,0 +1,79 @@
+//
+// Semigroups.jl
+// Copyright (C) 2026, James W. Swent
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#include "libsemigroups_julia.hpp"
+
+#include <libsemigroups/word-graph.hpp>
+
+#include <cstddef>
+#include <cstdint>
+
+namespace jlcxx {
+  template <>
+  struct IsMirroredType<libsemigroups::WordGraph<uint32_t>> : std::false_type {
+  };
+}  // namespace jlcxx
+
+namespace libsemigroups_julia {
+
+  void define_word_graph(jl::Module& m) {
+    using WordGraph_ = libsemigroups::WordGraph<uint32_t>;
+
+    auto type = m.add_type<WordGraph_>("WordGraph");
+
+    // Constructor: (num_nodes, out_degree)
+    type.constructor<std::size_t, std::size_t>();
+
+    // --- Read queries ---
+
+    type.method("number_of_nodes", [](WordGraph_ const& g) -> std::size_t {
+      return g.number_of_nodes();
+    });
+
+    type.method("out_degree", [](WordGraph_ const& g) -> std::size_t {
+      return g.out_degree();
+    });
+
+    type.method("target",
+                [](WordGraph_ const& g, uint32_t s, uint32_t a) -> uint32_t {
+                  return g.target(s, a);
+                });
+
+    // --- Mutators ---
+    // Getter `target(s, a)` and setter `target(s, a, t)` are same-name
+    // different-arity in C++; CxxWrap cannot reliably dispatch these, so the
+    // setter is bound under a distinct `target!` name. Returns void -- Julia
+    // does not need the *this chaining idiom.
+
+    type.method("target!",
+                [](WordGraph_& g, uint32_t s, uint32_t a, uint32_t t) {
+                  g.target(s, a, t);
+                });
+
+    // libsemigroups' target(s, a, t) rejects t = UNDEFINED (typemax) as
+    // out-of-range; clearing an edge requires the distinct `remove_target`
+    // entry point. Julia's `target!(g, s, a, UNDEFINED)` dispatches here.
+    type.method("remove_target!", [](WordGraph_& g, uint32_t s, uint32_t a) {
+      g.remove_target(s, a);
+    });
+
+    type.method("add_nodes!",
+                [](WordGraph_& g, std::size_t n) { g.add_nodes(n); });
+  }
+
+}  // namespace libsemigroups_julia

docs/make.jl

@@ -38,6 +38,7 @@ makedocs(;
             "Constants" => "data-structures/constants/index.md",
             "Orders" => "data-structures/order.md",
             "Words" => "data-structures/word-range.md",
+            "Word Graphs" => "data-structures/word-graph.md",
             "Elements" => [
                 "Overview" => "data-structures/elements/index.md",
                 "Transformations" => [

docs/src/data-structures/word-graph.md

@@ -0,0 +1,31 @@
+# The WordGraph type
+
+This page contains the documentation of the type [`WordGraph`](@ref
+Semigroups.WordGraph), a representation of a word graph over an alphabet
+of fixed out-degree.
+
+```@docs
+Semigroups.WordGraph
+```
+
+## Contents
+
+| Function                                                                                                   | Description                                                          |
+| ---------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------- |
+| [`WordGraph`](@ref Semigroups.WordGraph(::Integer, ::Integer))                                             | Construct from number of nodes and out degree.                       |
+| [`number_of_nodes`](@ref Semigroups.number_of_nodes(::WordGraph))                                          | Returns the number of nodes.                                         |
+| [`out_degree`](@ref Semigroups.out_degree(::WordGraph))                                                    | Returns the out-degree.                                              |
+| [`target`](@ref Semigroups.target(::WordGraph, ::Integer, ::Integer))                                      | Get the target of the edge with given source node and label.         |
+| [`target!`](@ref Semigroups.target!(::WordGraph, ::Integer, ::Integer, ::Integer))                         | Set the target of the edge with given source node and label.         |
+| [`add_nodes!`](@ref Semigroups.add_nodes!(::WordGraph, ::Integer))                                         | Add a number of new nodes.                                           |
+
+## Full API
+
+```@docs
+Semigroups.WordGraph(::Integer, ::Integer)
+Semigroups.number_of_nodes(::WordGraph)
+Semigroups.out_degree(::WordGraph)
+Semigroups.target(::WordGraph, ::Integer, ::Integer)
+Semigroups.target!(::WordGraph, ::Integer, ::Integer, ::Integer)
+Semigroups.add_nodes!(::WordGraph, ::Integer)
+```

src/Semigroups.jl

@@ -66,6 +66,7 @@ include("report.jl")
 include("runner.jl")
 include("order.jl")
 include("word-range.jl")
+include("word-graph.jl")
 
 # High-level element types
 include("bmat8.jl")
@@ -107,6 +108,9 @@ export order, set_order!, set_upper_bound!, set_min!, set_max!
 export number_of_words, random_word
 export next!, at_end, valid, init!, size_hint, upper_bound
 
+# WordGraph
+export WordGraph, number_of_nodes, out_degree, target, target!, add_nodes!
+
 # Transformation types and functions
 export Transf, PPerm, Perm
 export degree, rank, image, domain, inverse