Update README for JSON inputs

README.org

@@ -15,17 +15,28 @@ This program can be used to generate arbitrary L-systems. It supports:
 + personalized angle and segment length for the representation
 + push ('[') and pop (']') operations
 
-** ~LSystem~ data type
+** L-systems
 
-An L-system consists of:
-+ the L-system itself:
-  + an alphabet
-  + an axiom (i.e. the starting point)
-  + a set of rewriting rules (represented as a list of tuples)
-+ rules to transform it into a graphical representation:
-  + an angle and a length
-  + a set of representation rules (which symbols mean "draw forward",
-    "turn left", "pop a position", etc.)
+*** ~LSystem~ data type
+
+ An L-system consists of:
+ + the L-system itself:
+   + an alphabet
+   + an axiom (i.e. the starting point)
+   + a set of rewriting rules (represented as a list of tuples)
+ + rules to transform it into a graphical representation:
+   + an angle and a length
+   + a set of representation rules (which symbols mean "draw forward",
+     "turn left", "pop a position", etc.)
+
+*** JSON format for L-systems
+
+L-systems can be specified using a straightforward JSON encoding. See
+the =examples/= folder for examples.
+
+Note that the ~rules~ and ~representation~ keys are associated to
+arrays of arrays in JSON. ~angle~ and ~distance~ are
+numbers. Everything else should be a string.
 
 ** Building and running
 
@@ -34,7 +45,7 @@ You will need [[https://docs.haskellstack.org/][Stack]].
 From the repository, run:
 #+BEGIN_SRC sh
 stack build
-stack exec lsystems-exe
+stack exec lsystems-exe -- examples/penroseP3.json
 #+END_SRC
 
 This will open a window, where you can move around using the mouse and
@@ -51,22 +62,22 @@ command-line arguments, see the output of ~--help~:
 #+BEGIN_SRC 
 lsystems -- Generate L-systems
 
-Usage: lsystems-exe [LSYSTEM] [-n|--iterations N] [-c|--color R,G,B]
-                    [-w|--white-background] [-l|--list-lsystems]
+Usage: lsystems-exe FILENAME [-n|--iterations N] [-c|--color R,G,B]
+                    [-w|--white-background]
   Generate and draw an L-system
 
 Available options:
-  LSYSTEM                  L-system to generate (default: penroseP3)
+  FILENAME                 JSON file specifying an L-system
   -n,--iterations N        Number of iterations (default: 5)
   -c,--color R,G,B         Foreground color RGBA
                            (0-255) (default: RGBA 1.0 1.0 1.0 1.0)
   -w,--white-background    Use a white background
-  -l,--list-lsystems       List all available L-systems
   -h,--help                Show this help text
 #+END_SRC
 
+** Examples
 
-** Examples provided
+Examples are provided in the =examples/= directory.
 
 *** Space-filling curves