diff --git a/deques.ml b/deques.ml
index d0156da..4c782a1 100644
--- a/deques.ml
+++ b/deques.ml
@@ -40,37 +40,100 @@ module ColorOrder = struct
   type nonrec 'a yellow = [`Yellow of 'a yellow]
   type nonrec 'a red    = [`Red    of 'a red]
   
-  type 'a le_green  = [ | 'a green | 'a yellow | 'a red]
-  type 'a le_yellow = [ |            'a yellow | 'a red]
-  type 'a le_red    = [ |                        'a red]
+  type 'a leGreen  = [ | 'a green | 'a yellow | 'a red]
+  type 'a leYellow = [ |            'a yellow | 'a red]
+  type 'a leRed    = [ |                        'a red]
   
-  type 'a ge_green  = [ | 'a green                     ]
-  type 'a ge_yellow = [ | 'a green | 'a yellow         ]
-  type 'a ge_red    = [ | 'a green | 'a yellow | 'a red]
+  type 'a geGreen  = [ | 'a green                     ]
+  type 'a geYellow = [ | 'a green | 'a yellow         ]
+  type 'a geRed    = [ | 'a green | 'a yellow | 'a red]
 end
 open ColorOrder
 
-type 'a nested_deque = [`Some of ('a * 'a) deque]
-type ('prefix, 'nested, 'suffix) deque2 = {
-  prefix: 'prefix;
-  child:  'nested;
-  suffix: 'suffix;
+type 'a nestedDeque = [`Some of ('a * 'a) deque]
+type ('prefix, 'substack, 'stack, 'suffix) deque2 = {
+  prefix:   'prefix;
+  substack: 'substack;
+  stack:    'stack;
+  suffix:   'suffix;
 }
 
-(** jacm-final.pdf p.9 (585) §4.1 media 60 230 368 48 *)
-type ('a, 'color, 'le_color) colored_buffer =
-  [  `Full of ('color,     'a nested_deque, 'le_color)  deque2
-   | `L    of ('a buffer0, [`None],         'le_color)  deque2
-   | `R    of ('color,     [`None],         'a buffer0) deque2]
-type 'a greenDeque  = [`Green  of ('a, 'a green,  'a le_green)  colored_buffer]
-type 'a yellowDeque = [`Yellow of ('a, 'a yellow, 'a le_yellow) colored_buffer]
-type 'a redDeque    = [`Red    of ('a, 'a red,    'a le_red)    colored_buffer]
 
-(* TODO: color constraints for the root and collapsing of intermediate sequences of yellow *)
-type 'a deque3 = ['a greenDeque | 'a yellowDeque | 'a redDeque]
+
+
+
+
+(** jacm-final.pdf p.9 (585) §4.1 media 60 230 368 48 *)
+module ColoredDeques = struct
+  type ('a, 'color, 'leColor) coloredDeque =
+    [  `Full of ('color,     'a nestedDeque, 'leColor)  deque2 (* TODO: the nested deque should be a recursive type *)
+     (* TODO: `L and `R should be merged into a single case + constructor inside, and the empty parts the info deleted *)
+     | `L    of ('a buffer0, [`None],         'leColor)  deque2
+     | `R    of ('color,     [`None],         'a buffer0) deque2] constraint 'xyz = 'xyz (* TODO: use constraint to allow or forbid the empty child (L/R) case for yellow. *)
+  type 'a greenDeque  = [`Green  of ('a, 'a green,  'a leGreen)  coloredDeque]
+  type 'a yellowDeque = [`Yellow of ('a, 'a yellow, 'a leYellow) coloredDeque]
+  type 'a redDeque    = [`Red    of ('a, 'a red,    'a leRed)    coloredDeque]
+end
+open ColoredDeques
+
+
+
+
+
+
+
+(** jacm-final.pdf p.9 (585) §4.1 media 60 230 368 48 *)
+module ColoredDeques2 = struct
+  type ('a, 'color, 'leColor, 'substack, 'stack) coloredDeque =
+    [  `Full of ('color,     'substack, 'stack,    'leColor) deque2]
+  (** The astute reader will notice that if the child of a deque is empty,
+     then it is the first (deepest) element on the stack. Therefore, the cases
+     considering that the colour of a deque is that of its only non-empty
+     buffer, if its child is also empty, apply only to the first element of the
+     stack. *)
+  type ('a, 'color, 'leColor, 'substack, 'stack) coloredLRDeque = [
+       ('a, 'color, 'leColor, 'substack, 'stack) coloredDeque
+     | `L    of ('a buffer0, [`None],   [`None],   'leColor) deque2
+     | `R    of ('color,     [`None],   [`None], 'a buffer0) deque2]
+
+  (* "Error: The type constructor yellowDeque is not yet completely defined"
+     if we don't use a fixup: all expanded cases in […|…] have to be
+     completely defined (or wrapped with a `X so that they need not be
+     substituted) *)
+  type 'a greenDeque  = ('a, 'a green,  'a leGreen,  [`None|`Yellow of 'a yellowDeque], [`None | `Green of 'a greenDeque |   `Red of 'a   redDeque]) coloredDeque
+  and  'a yellowDeque = ('a, 'a yellow, 'a leYellow, [`None|`Yellow of 'a yellowDeque], [`None]) coloredDeque
+  and  'a redDeque    = ('a, 'a red,    'a leRed,    [`None|`Yellow of 'a yellowDeque], [`None | `Green of 'a greenDeque]) coloredDeque
+end
+open ColoredDeques2
+
+module ColoredDequesFixup = struct
+  type nonrec 'a greenDeque  = [`Green  of 'a greenDeque ]
+  and         'a yellowDeque = [`Yellow of 'a yellowDeque]
+  and         'a redDeque    = [`Red    of 'a redDeque   ]
+end
+open ColoredDequesFixup
+
 
 (* jacm-final.pdf p.8 / 584 §4.1 60 480 368 36 *)
 
 (* let rec child i d =
      if i = 0 then d
      else child (i - 1) d.child *)
+
+(* TODO: what is the state of the `None once there are two pointers? *)
+(* TODO: Problem: a yellow at the bottom of its substack needs to know what's beneath to know
+   if the "no child + one empty buffer" case is allowed. *)
+(* TODO: show the naïve (wrong) version here. *)
+
+(* type ('a, 'color, 'leColor, 'nested) colored9 =
+ *   [  `Full of ('color,     'nestedSubstack, 'nestedStack, 'leColor)  deque2
+ *    | `L    of ('a buffer0, [`None],          'nestedStack, 'leColor)  deque2
+ *    | `R    of ('color,     [`None],          'nestedStack, 'a buffer0) deque2]
+ * type 'a greenDeque  = [`Green  of ('a, 'a green,  'a leGreen)  colored9]
+ * type 'a yellowDeque = [`Yellow of ('a, 'a yellow, 'a leYellow) colored9]
+ * type 'a redDeque    = [`Red    of ('a, 'a red,    'a leRed)    colored9] *)
+
+(* type 'a yellowDeque    = [`Yellow of ('a, 'a yellow, 'a leYellow, [`Some of ('a * 'a) nonYellowDeque])   coloredDeque]
+ * and  'a greenDeque     = [`Green  of ('a, 'a green,  'a leGreen,  [`Some of ('a * 'a) yellowDeque list]) coloredDeque]
+ * and  'a redDeque       = [`Red    of ('a, 'a red,    'a leRed,    [`Some of ('a * 'a) yellowDeque list]) coloredDeque]
+ * and  'a nonYellowDeque = ['a greenDeque | 'a redDeque] *)