From d4c73bf4832967ff67f92ceb5b28f686aea24c79 Mon Sep 17 00:00:00 2001
From: Sumi Sera <ragdgamal77@gmail.com>
Date: Wed, 14 Oct 2026 14:44:05 +0100
Subject: [PATCH 1/2] Created a LAD serialiser and deserialiser to convert to
 and from digraphs and LAD format

---
 gap/io.gd |  2 ++
 gap/io.gi | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/gap/io.gd b/gap/io.gd
index 66d6870e8..30235752a 100644
--- a/gap/io.gd
+++ b/gap/io.gd
@@ -62,3 +62,5 @@ DeclareOperation("DIMACSString", [IsDigraph]);
 DeclareGlobalFunction("WritePlainTextDigraph");
 DeclareGlobalFunction("DreadnautString");
 DeclareGlobalFunction("DigraphPlainTextLineEncoder");
+DeclareOperation("LADString", [IsDigraph]);
+DeclareOperation("DigraphFromLADString", [IsString]);
\ No newline at end of file
diff --git a/gap/io.gi b/gap/io.gi
index cbb2297de..460856bc8 100644
--- a/gap/io.gi
+++ b/gap/io.gi
@@ -2602,3 +2602,55 @@ end);
 
 InstallMethod(PlainTextString, "for a digraph", [IsDigraph],
 D -> DigraphPlainTextLineEncoder("  ", " ", -1)(D));
+
+InstallMethod(LADString, "for a digraph", [IsDigraph],
+function(D)
+  local result, nbs, v;
+  if IsMultiDigraph(D) then
+    ErrorNoReturn("the argument <D> must not have multiple edges");
+  elif DigraphHasLoops(D) then
+    ErrorNoReturn("the arguement <D> must not have loops");
+  fi;
+  result := StringFormatted("{}\n", DigraphNrVertices(D));
+  for nbs in OutNeighbours(D) do
+    Append(result, String(Length(nbs)));
+    for v in SortedList(nbs) do
+      Append(result, " ");
+      Append(result, String(v-1));
+    od;
+    Append(result, "\n");
+  od;
+  return result;
+end);
+
+InstallMethod(DigraphFromLADString, "for a String", [IsString],
+function(s)
+  
+  #validating and parsing the string into seperate lines
+  local lines, n, nbs, line, i, v;
+  lines := Filtered(SplitString(s, "\n"), x -> not IsEmpty(x));
+  if IsEmpty(lines) then
+    ErrorNoReturn("the argument <s> must be a non-empty string");
+  fi;
+  n := Int(NormalizedWhitespace(lines[1]));
+  if n = fail or n < 0 or Length(lines) <> n + 1 then
+    ErrorNoReturn("the first line of <s> must be the number of vertices followed by one line per vertex");
+  fi;
+
+  #Convert LAD to Digraph
+  nbs := [];
+  for i in [1 .. n] do
+    line := List(SplitString(NormalizedWhitespace(lines[i+1]), " "), Int);
+    if IsEmpty(line) or line[1] <> Length(line) - 1 then
+      ErrorNoReturn("line ", i+1, " of <s> is not valid");
+    fi;
+    Remove(line, 1);
+    for v in line do
+      if v < 0 or v >= n then
+        ErrorNoReturn("line ", i+1, " of <s> has a vertex out of range");
+      fi;
+    od;
+    Add(nbs, line + 1); #converting from 0 indexed to 1 indexed
+  od;
+  return ConvertToImmutableDigraphNC(nbs);
+  end);
\ No newline at end of file

From 263a3ce6a2ba738d0026ef563c836d9971fbbf3c Mon Sep 17 00:00:00 2001
From: Sumi Sera <ragdgamal77@gmail.com>
Date: Wed, 14 Oct 2026 15:09:58 +0100
Subject: [PATCH 2/2] fix styling issues

---
 gap/io.gi | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/gap/io.gi b/gap/io.gi
index 460856bc8..c3514e94e 100644
--- a/gap/io.gi
+++ b/gap/io.gi
@@ -2609,14 +2609,14 @@ function(D)
   if IsMultiDigraph(D) then
     ErrorNoReturn("the argument <D> must not have multiple edges");
   elif DigraphHasLoops(D) then
-    ErrorNoReturn("the arguement <D> must not have loops");
+    ErrorNoReturn("the argument <D> must not have loops");
   fi;
   result := StringFormatted("{}\n", DigraphNrVertices(D));
   for nbs in OutNeighbours(D) do
     Append(result, String(Length(nbs)));
     for v in SortedList(nbs) do
       Append(result, " ");
-      Append(result, String(v-1));
+      Append(result, String(v - 1));
     od;
     Append(result, "\n");
   od;
@@ -2625,8 +2625,7 @@ end);
 
 InstallMethod(DigraphFromLADString, "for a String", [IsString],
 function(s)
-  
-  #validating and parsing the string into seperate lines
+  # validating and parsing the string into separate lines
   local lines, n, nbs, line, i, v;
   lines := Filtered(SplitString(s, "\n"), x -> not IsEmpty(x));
   if IsEmpty(lines) then
@@ -2634,23 +2633,24 @@ function(s)
   fi;
   n := Int(NormalizedWhitespace(lines[1]));
   if n = fail or n < 0 or Length(lines) <> n + 1 then
-    ErrorNoReturn("the first line of <s> must be the number of vertices followed by one line per vertex");
+    ErrorNoReturn("the first line of <s> must be the number of vertices ",
+                  "followed by one line per vertex");
   fi;
 
-  #Convert LAD to Digraph
+  # Convert LAD to Digraph
   nbs := [];
   for i in [1 .. n] do
-    line := List(SplitString(NormalizedWhitespace(lines[i+1]), " "), Int);
+    line := List(SplitString(NormalizedWhitespace(lines[i + 1]), " "), Int);
     if IsEmpty(line) or line[1] <> Length(line) - 1 then
-      ErrorNoReturn("line ", i+1, " of <s> is not valid");
+      ErrorNoReturn("line ", i + 1, " of <s> is not valid");
     fi;
     Remove(line, 1);
     for v in line do
       if v < 0 or v >= n then
-        ErrorNoReturn("line ", i+1, " of <s> has a vertex out of range");
+        ErrorNoReturn("line ", i + 1, " of <s> has a vertex out of range");
       fi;
     od;
-    Add(nbs, line + 1); #converting from 0 indexed to 1 indexed
+    Add(nbs, line + 1);  # converting from 0 indexed to 1 indexed
   od;
   return ConvertToImmutableDigraphNC(nbs);
-  end);
\ No newline at end of file
+end);
\ No newline at end of file