From bbd1d8f317095a435711b8ef001b20c4aab0e61f Mon Sep 17 00:00:00 2001
From: Hraban Luyat <hraban@0brg.net>
Date: Fri, 27 May 2011 15:57:57 +0000
Subject: [PATCH 1/2] Mirror 'root' functionality for leaf nodes

Defines two new functions: graph-leafs and leafp. These are similar to
graph-roots and rootp but act on leaf nodes instead.
---
 dev/api.lisp     | 11 +++++++++++
 dev/graph.lisp   |  8 ++++++++
 dev/package.lisp |  2 ++
 3 files changed, 21 insertions(+)

diff --git a/dev/api.lisp b/dev/api.lisp
index 32231b3..fc92992 100644
--- a/dev/api.lisp
+++ b/dev/api.lisp
@@ -550,11 +550,22 @@ as a source. [?? Could be a defun]."))
   are out-going\). (cf. rootp) [?? could be a defun]"))
 
 
+(defgeneric graph-leafs (graph)
+  (:documentation "Returns a list of the leafs of graph. A leaf is
+  defined as a vertex with no target edges \(i.e., all of the edges
+  are incoming\). (cf. targetp) [?? could be a defun]"))
+
+
 (defgeneric rootp (vertex)
   (:documentation "Returns true if `vertex` is a root vertex \(i.e.,
   it has no incoming \(source\) edges\)."))
 
 
+(defgeneric leafp (vertex)
+  (:documentation "Returns true if `vertex` is a leaf vertex \(i.e.,
+  it has no outgoing \(target\) edges\)."))
+
+
 (defgeneric find-vertex-if (thing predicate &key key)
   (:documentation "Returns the first vertex in `thing` for which the
   `predicate` function returns non-nil. If the `key` is supplied, then
diff --git a/dev/graph.lisp b/dev/graph.lisp
index 8114715..f2d6671 100644
--- a/dev/graph.lisp
+++ b/dev/graph.lisp
@@ -677,11 +677,19 @@ something is putting something on the vertexes plist's
   (collect-elements (graph-vertexes graph) :filter #'rootp))
 
 
+(defmethod graph-leafs ((graph basic-graph))
+  (collect-elements (graph-vertexes graph) :filter #'leafp))
+
+
 (defmethod rootp ((vertex basic-vertex))
   ;;?? this is inefficient in the same way that (zerop (length <list>)) is...
   (zerop (target-edge-count vertex)))
 
 
+(defmethod leafp ((vertex basic-vertex))
+  (zerop (source-edge-count vertex)))
+
+
 (defmethod find-vertex-if ((graph basic-graph) fn &key key)
   (iterate-vertexes graph
                     (lambda (v)
diff --git a/dev/package.lisp b/dev/package.lisp
index 83e707f..5181ee1 100644
--- a/dev/package.lisp
+++ b/dev/package.lisp
@@ -46,7 +46,9 @@ DISCUSSION
    #:target-edge-count             ; vertex
    
    #:rootp                         ; vertex
+   #:leafp                         ; vertex
    #:graph-roots                   ; graph
+   #:graph-leafs                   ; graph
    
    #:topological-sort              ; graph
    #:depth                         ; graph | vertex

From c6e58815988deb8933dc644de0e3b1bbc703a393 Mon Sep 17 00:00:00 2001
From: Hraban Luyat <hraban@0brg.net>
Date: Mon, 14 Aug 2023 18:27:58 -0400
Subject: [PATCH 2/2] spelling leafs -> leaves
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

I think I originally wanted to be consistent with some weird thing? But
obviously it’s better to follow English grammar.
---
 dev/api.lisp     | 4 ++--
 dev/graph.lisp   | 2 +-
 dev/package.lisp | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/dev/api.lisp b/dev/api.lisp
index fc92992..6c31235 100644
--- a/dev/api.lisp
+++ b/dev/api.lisp
@@ -550,8 +550,8 @@ as a source. [?? Could be a defun]."))
   are out-going\). (cf. rootp) [?? could be a defun]"))
 
 
-(defgeneric graph-leafs (graph)
-  (:documentation "Returns a list of the leafs of graph. A leaf is
+(defgeneric graph-leaves (graph)
+  (:documentation "Returns a list of the leaves of graph. A leaf is
   defined as a vertex with no target edges \(i.e., all of the edges
   are incoming\). (cf. targetp) [?? could be a defun]"))
 
diff --git a/dev/graph.lisp b/dev/graph.lisp
index f2d6671..b27daa6 100644
--- a/dev/graph.lisp
+++ b/dev/graph.lisp
@@ -677,7 +677,7 @@ something is putting something on the vertexes plist's
   (collect-elements (graph-vertexes graph) :filter #'rootp))
 
 
-(defmethod graph-leafs ((graph basic-graph))
+(defmethod graph-leaves ((graph basic-graph))
   (collect-elements (graph-vertexes graph) :filter #'leafp))
 
 
diff --git a/dev/package.lisp b/dev/package.lisp
index 5181ee1..429d3f0 100644
--- a/dev/package.lisp
+++ b/dev/package.lisp
@@ -48,7 +48,7 @@ DISCUSSION
    #:rootp                         ; vertex
    #:leafp                         ; vertex
    #:graph-roots                   ; graph
-   #:graph-leafs                   ; graph
+   #:graph-leaves                  ; graph
    
    #:topological-sort              ; graph
    #:depth                         ; graph | vertex