1 files changed, 56 insertions, 0 deletions
diff --git a/INTERNALS.rst b/INTERNALS.rst
new file mode 100644
index 0000000..2178de1
--- /dev/null
+++ b/INTERNALS.rst
@@ -0,0 +1,56 @@
+Words are read into two datastructures:
+
+To illustrate these datastructures, we will suppose the following input text::
+
+    a b c d  e    f g h
+      a b a    d
+    f g h
+
+    z
+
+The main  datastructures are:
+
+- An array indexed by their order of appearance.
+
+  This is not purely a string array, words are structures which contain the
+  following informations:
+
+  - the display string which can be shorter than the original string;
+  - the original string;
+  - a flag indicating the this is the last word in a paragraph like
+    **h**, **d**, **h** and **z** if our example test;
+  - positional infomations: column start, column end end an number of
+    multibyes between the two.
+
+  The following text will be put in the word array::
+
+
+                                last=1          last=1    last=1 last=1
+                                  |               |           |   |
+    +---+---+---+---+---+---+---+-v-+---+---+---+-v-+---+---+-v-+-v-+
+    | a | b | c | d | e | f | g | h | a | b | a | d | f | g | h | z |
+    +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+      0   1   . . .                                       13  14  15
+
+- A Ternary Search Treee (TST) which store their position in the array
+  and all their furure positions if their appear multiple times.
+
+  In the TST tree, index lists are attached to the input words::
+
+      +---+---+----+                 
+    a | 0 | 8 | 10 |                 
+      +---+---+----+
+
+      +---+---+                 
+    b | 1 | 9 |                 
+      +---+---+
+
+      +---+                
+    c | 2 |                 
+      +---+
+
+  and so on.
+
+  This TST is used when searching a word using the ``/`` command or when using
+  the ``-s`` commandline option.
+