Documentation: directly use ref object + fields (#6598)

5 files changed, 48 insertions, 37 deletions

diff --git a/doc/manual/generics.txt b/doc/manual/generics.txt
index cceea33c0..1ba62bb5c 100644
--- a/doc/manual/generics.txt
+++ b/doc/manual/generics.txt
@@ -9,26 +9,26 @@ The following example shows a generic binary tree can be modelled:
 
 .. code-block:: nim
   type
-    BinaryTreeObj[T] = object    # BinaryTreeObj is a generic type with
-                                 # with generic param ``T``
-      le, ri: BinaryTree[T]      # left and right subtrees; may be nil
-      data: T                    # the data stored in a node
-    BinaryTree[T] = ref BinaryTreeObj[T] # a shorthand for notational convenience
+    BinaryTree*[T] = ref object # BinaryTree is a generic type with
+                                # generic param ``T``
+      le, ri: BinaryTree[T]     # left and right subtrees; may be nil
+      data: T                   # the data stored in a node
 
-  proc newNode[T](data: T): BinaryTree[T] = # constructor for a node
+  proc newNode*[T](data: T): BinaryTree[T] =
+    # constructor for a node
     new(result)
     result.data = data
 
-  proc add[T](root: var BinaryTree[T], n: BinaryTree[T]) =
+  proc add*[T](root: var BinaryTree[T], n: BinaryTree[T]) =
+    # insert a node into the tree
     if root == nil:
       root = n
     else:
       var it = root
       while it != nil:
-        var c = cmp(it.data, n.data) # compare the data items; uses
-                                     # the generic ``cmp`` proc that works for
-                                     # any type that has a ``==`` and ``<``
-                                     # operator
+        # compare the data items; uses the generic ``cmp`` proc
+        # that works for any type that has a ``==`` and ``<`` operator
+        var c = cmp(it.data, n.data)
         if c < 0:
           if it.le == nil:
             it.le = n
@@ -40,20 +40,28 @@ The following example shows a generic binary tree can be modelled:
             return
           it = it.ri
 
-  iterator inorder[T](root: BinaryTree[T]): T =
-    # inorder traversal of a binary tree
-    # recursive iterators are not yet implemented, so this does not work in
-    # the current compiler!
-    if root.le != nil: yield inorder(root.le)
-    yield root.data
-    if root.ri != nil: yield inorder(root.ri)
+  proc add*[T](root: var BinaryTree[T], data: T) =
+    # convenience proc:
+    add(root, newNode(data))
+
+  iterator preorder*[T](root: BinaryTree[T]): T =
+    # Preorder traversal of a binary tree.
+    # Since recursive iterators are not yet implemented,
+    # this uses an explicit stack (which is more efficient anyway):
+    var stack: seq[BinaryTree[T]] = @[root]
+    while stack.len > 0:
+      var n = stack.pop()
+      while n != nil:
+        yield n.data
+        add(stack, n.ri)  # push right subtree onto the stack
+        n = n.le          # and follow the left pointer
 
   var
-    root: BinaryTree[string]  # instantiate a BinaryTree with the type string
-  add(root, newNode("hallo")) # instantiates generic procs ``newNode`` and
-  add(root, newNode("world")) # ``add``
-  for str in inorder(root):
-    writeLine(stdout, str)
+    root: BinaryTree[string] # instantiate a BinaryTree with ``string``
+  add(root, newNode("hello")) # instantiates ``newNode`` and ``add``
+  add(root, "world")          # instantiates the second ``add`` proc
+  for str in preorder(root):
+    stdout.writeLine(str)
 
 
 Is operator
diff --git a/doc/manual/pragmas.txt b/doc/manual/pragmas.txt
index db7ce7e63..835b6909d 100644
--- a/doc/manual/pragmas.txt
+++ b/doc/manual/pragmas.txt
@@ -102,6 +102,14 @@ collector to not consider objects of this type as part of a cycle:
       left, right: Node
       data: string
 
+Or if we directly use a ref object:
+
+.. code-block:: nim
+  type
+    Node = ref object {.acyclic, final.}
+      left, right: Node
+      data: string
+
 In the example a tree structure is declared with the ``Node`` type. Note that
 the type definition is recursive and the GC has to assume that objects of
 this type may form a cyclic graph. The ``acyclic`` pragma passes the
diff --git a/doc/manual/type_sections.txt b/doc/manual/type_sections.txt
index af761c77e..12b2a11ac 100644
--- a/doc/manual/type_sections.txt
+++ b/doc/manual/type_sections.txt
@@ -5,8 +5,7 @@ Example:
 
 .. code-block:: nim
   type # example demonstrating mutually recursive types
-    Node = ref NodeObj # a traced pointer to a NodeObj
-    NodeObj = object
+    Node = ref object  # an object managed by the garbage collector (ref)
       le, ri: Node     # left and right subtrees
       sym: ref Sym     # leaves contain a reference to a Sym
 
diff --git a/doc/tut1.rst b/doc/tut1.rst
index be5cd8c11..6731efde9 100644
--- a/doc/tut1.rst
+++ b/doc/tut1.rst
@@ -1511,8 +1511,7 @@ operators perform implicit dereferencing operations for reference types:
 .. code-block:: nim
 
   type
-    Node = ref NodeObj
-    NodeObj = object
+    Node = ref object
       le, ri: Node
       data: int
   var
diff --git a/doc/tut2.rst b/doc/tut2.rst
index 0bb4c94e1..0636c4ed6 100644
--- a/doc/tut2.rst
+++ b/doc/tut2.rst
@@ -104,15 +104,14 @@ Example:
 
 .. code-block:: nim
   type
-    Node = ref NodeObj # a traced reference to a NodeObj
-    NodeObj = object
+    Node = ref object  # a reference to an object with the following field:
       le, ri: Node     # left and right subtrees
       sym: ref Sym     # leaves contain a reference to a Sym
 
     Sym = object       # a symbol
       name: string     # the symbol's name
       line: int        # the line the symbol was declared in
-      code: Node      # the symbol's abstract syntax tree
+      code: Node       # the symbol's abstract syntax tree
 
 
 Type conversions
@@ -155,8 +154,7 @@ An example:
       nkAdd,          # an addition
       nkSub,          # a subtraction
       nkIf            # an if statement
-    Node = ref NodeObj
-    NodeObj = object
+    Node = ref object
       case kind: NodeKind  # the ``kind`` field is the discriminator
       of nkInt: intVal: int
       of nkFloat: floatVal: float
@@ -482,11 +480,10 @@ containers:
 
 .. code-block:: nim
   type
-    BinaryTreeObj[T] = object # BinaryTree is a generic type with
-                              # with generic param ``T``
-      le, ri: BinaryTree[T]   # left and right subtrees; may be nil
-      data: T                 # the data stored in a node
-    BinaryTree*[T] = ref BinaryTreeObj[T] # type that is exported
+    BinaryTree*[T] = ref object # BinaryTree is a generic type with
+                                # generic param ``T``
+      le, ri: BinaryTree[T]     # left and right subtrees; may be nil
+      data: T                   # the data stored in a node
 
   proc newNode*[T](data: T): BinaryTree[T] =
     # constructor for a node