Add compose to tutorial.

examples/tutorial.hs

@@ -253,3 +253,41 @@ factorial x =
   if x == 0
     then 1
     else factorial (x - 1) * x
+
+{- Bonus section:
+
+The depth of an icon's application tree is called the nesting depth.
+For example, The icon representing "factorial (x - 1) * x" above has a nesting
+depth of 3.
+
+To reduce nesting depth, Glance has an icon that represents an argument applied
+to a composition of functions.
+
+For example:
+y = f (g x)
+-}
+y = f (g x)
+
+{-
+Glance figures out automatically when to use the compose icon in order to
+reduce the nesting depth.
+
+For example, if we slightly rewrite the factorial function above, Glance
+uses a compose icon for the else expression.
+
+To enable the compose icon, we change the expression
+factorial (x - 1) * x
+to
+x * factorial (x - 1)
+
+Notice that the nesting level has been reduced from 3 to 2.
+
+--factorial x =
+--  if x == 0
+--    then 1
+--    else x * factorial (x - 1)
+-}
+factorial x =
+  if x == 0
+    then 1
+    else x * factorial (x - 1)

todo.txt

@@ -1,27 +1,27 @@
 -- TODO Now --
-Add compose to the tutorial.
 
 -- TODO Later --
 -- Add documentation.
 
 -- Testing todos:
-Fix the arrowheads being too big for SyntaxGraph darwings.
+Fix the arrowheads being too big for SyntaxGraph drawings.
 
 -- Visual todos:
 -- Make an icon font/library with labeled ports. E.g. the apply icon would have text labels "function", "result", "arg 0", "arg 1", etc.
--- Don't rotate text and nested icons, give them rectangualar bounding boxes in GraphViz. (Perhaps use a typeclass for isRotateAble)
+-- Don't rotate text and nested icons, give them rectangular bounding boxes in GraphViz. (Perhaps use a typeclass for isRotateAble)
 -- Give lines a black border to make line crossings easier to see.
 -- Give lines that cross the border of a lambda function a special color.
 -- Line intersections should have a small circle. This could probably be done with
 -- a line ending.
 -- Let each bool, value pair in Guard icon be flipped to reduce line crossings. Do the same for case.
--- Let lines connect to ports in multiple locations (eg. case value, or guard result)
--- Use different line styles (eg. dashed, solid, wavy) in addition to colors
+-- Let lines connect to ports in multiple locations (e.g. case value, or guard result)
+-- Use different line styles (e.g. dashed, solid, wavy) in addition to colors
 
 -- Translate todos:
+Fix applyComposeScore in Translate.hs not counting expressions that nest via reference. May need to move compose generation to after translate.
 
 -- Fix test case x of {0 -> 1; y -> y}.
 -- Add proper RecConstr, and RecUpdate support.
 -- Eliminate BranchIcon in Alts.
--- Eliminate BranchIcon for the identity funciton "y x = x"
+-- Eliminate BranchIcon for the identity function "y x = x"
 -- Special case for otherwise.