From cb7ceda00cb6c0f21bdf475ee10d2125ecdaeff2 Mon Sep 17 00:00:00 2001
From: Antonov548 <antonov5551998@gmail.com>
Date: Fri, 27 Oct 2023 14:17:57 +0200
Subject: [PATCH] is_tree: separate `VERTEX_ROOT` type

---
 R/aaa-auto.R                    |  9 ++++-----
 tools/stimulus/functions-R.yaml |  4 ++++
 tools/stimulus/types-RR.yaml    | 13 +++++++++++++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/R/aaa-auto.R b/R/aaa-auto.R
index 2a2aad6847..b43d7d7c03 100644
--- a/R/aaa-auto.R
+++ b/R/aaa-auto.R
@@ -3791,13 +3791,12 @@ is_tree_impl <- function(graph, mode=c("out", "in", "all", "total"), details=FAL
   on.exit( .Call(R_igraph_finalizer) )
   # Function call
   res <- .Call(R_igraph_is_tree, graph, mode)
-    if (!details) {
-    res <- res$res
-} else if (vcount(graph) == 0) {
-    # FIXME: Better handled in rinterface_extra.c, or via a dedicated type?
-  } else if (igraph_opt("return.vs.es")) {
+  if (igraph_opt("return.vs.es") && vcount(graph) != 0) {
     res$root <- create_vs(graph, res$root)
   }
+  if (!details) {
+    res <- res$res
+  }
   res
 }
 
diff --git a/tools/stimulus/functions-R.yaml b/tools/stimulus/functions-R.yaml
index d3386d0ef4..63d06824fc 100644
--- a/tools/stimulus/functions-R.yaml
+++ b/tools/stimulus/functions-R.yaml
@@ -1125,6 +1125,10 @@ igraph_get_stochastic_sparsemat:
 igraph_hrg_dendrogram:
     PARAMS: OUT GRAPH graph, HRG hrg
 
+igraph_is_tree:
+    PARAMS: GRAPH graph, PRIMARY OUT BOOLEAN res, OPTIONAL OUT VERTEX_ROOT root, NEIMODE mode=OUT
+    DEPS: root ON graph
+
 #######################################
 # Coloring
 #######################################
diff --git a/tools/stimulus/types-RR.yaml b/tools/stimulus/types-RR.yaml
index c8bd743886..c4abfd92a3 100644
--- a/tools/stimulus/types-RR.yaml
+++ b/tools/stimulus/types-RR.yaml
@@ -130,6 +130,19 @@ VERTEX:
               %I% <- create_vs(%I1%, %I%)
             }
 
+VERTEX_ROOT:
+    CALL: '%I%-1'
+    INCONV: |-
+        %I% <- as_igraph_vs(%I1%, %I%)
+        if (length(%I%) == 0) {
+          stop("No vertex was specified")
+        }
+    OUTCONV:
+        OUT: |-
+            if (igraph_opt("return.vs.es") && vcount(%I1%) != 0) {
+              %I% <- create_vs(%I1%, %I%)
+            }
+
 VERTEX_SELECTOR:
     CALL: '%I%-1'
     DEFAULT: