On Wed, 2010-03-24 at 21:33 -0400, Ronald Guida wrote: > Those are some very interesting visual languages, Miguel! > > I remember drawing some diagrams when I was teaching myself Haskell, > but I never actually tried to create a formal visual language. Since > my background is in hardware engineering, I would naturally gravitate > toward schematic diagrams. I am also familiar with the graphical > programming language of LabView. > > After reading Miguel's exposition, I thought about how I might draw a > picture of map1. > > map1 :: (a -> b) -> [a] -> [b] > map1 f [] = [] > map1 f (x:xs) = (f x) : map1 f xs > > map1.png > (Image created with Inkscape) > > Here is what I'm thinking: > * Green boxes represent inputs and outputs. > * Inputs are always on the left, outputs are always on the right. > * Inputs appear in top-to-bottom order. > * Data always flows left to right. > * Arrows represent data flow. > * A named white rectangle represents application of the named > function. > * A gray rectangle represents a function that arrives through data > flow. > * A filled-in arrowhead means the data "in" the arrow is to be > "unpacked" and used as a function. > * A named light-blue rectangle (such as on the left, with a colon in > it) represents a pattern match operation. > > In thinking about this, I can sense that there are MANY issues with > using a visual language to represent Haskell. Some issues I can think > of: > * How to represent pattern matching? > * How to represent partial application? > * How to represent data types or class constraints in the diagram? > * How to represent a list comprehension or a do statement? (These > might require special visual syntax) > * Will the data flow always take the form of a directed acyclic graph, > so that data never has to flow right-to-left? (Perhaps there's a way > to "tie the knot" and get a cycle in the data flow graph.)
myfix f = let x = f x in x
f -------\
|
v
/->X-X--+-------->
| |
\---<---/
Unless we rewrite it into:
myfix' f = f (myfix' f)
f ----+-------------------\
| |
| v
\->X myfix' X----->X-X---->
> * Whether to create special symbols for certain commonly used
> functions? (In digital circuit schematics, AND, OR, and NOT gates have
> special symbols, but most compound circuits are represented with
> labeled rectangles.)
>
> Also, if I want to automatically generate an image from a Haskell
> function, then my image generator needs to automatically place and
> route all those boxes.
>
> I'll have to give more thought to the other versions of map, and maybe
> make some more diagrams.
>
> -- Ron
Regards
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