# Visualizing Data Structures with Vip Today we will talk about a nice add-on which allows to draw data structures and basic ASCII forms with Vip. This function serves basically for didactic purposes, i. e. highlighting the **PicoLisp equivalence of code and data** and internal representation of data, but can also be handy to draw simple overview charts. ---------------- ### Drawing data structures with Vip As you might remember, all PicoLisp data strctures are made from **cells** ([read here](https://picolisp-blog.hashnode.dev/concepts-and-data-types) if that's new for you). However it can be difficult to imagine what this actually looks like. Vip has a handy little feature that converts a given list into a cell structure. First of all, we need to add the following line to the top of our file (let's call it ``Symbols``: ``` # VIP @lib/vip/draw.l ``` This loads the ``draw.l`` library. Now reload the Vip with ``:e``, and you will see that the REPL has loaded the ``view>`` method which is inside the ``draw.l`` library: ![pic1.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287550821/IBbslJu4M.png) --------------------- Now if you press ``v``, a new temporay file will open up. You can see it's a new one because the bottom line changes from "1/1" to "2/2 ~/.pil/tmp/". You can toggle between the original and the new window with ``F5`` and ``F6``, however it is recommended to split the screen instead: ------------------ ### Splitting the screen horizontally (recommended) In order to split the screen horizontally, press ``qs`` in the editing mode. ![pic2.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287564278/iKxXhpl812.png) Now you have the same file open in the upper and lower half. You can jump between them with ``qj`` and ``qk``, and adjust the relative sizes with ``+`` and ``-``. ------------- Press ``F5`` in the upper window so that you get the original ``Symbols`` file in the upper part and the temporary file in the lower part. ![pic3.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287573098/zegvSihMQ.png) ------------------- ### The ``cells`` / ``cell`` function Now we can play with it. ``cells`` function take three arguments: start position in x and y (upper left corner is 1, 1) and the symbol to be drawn. Let's draw a list by adding this to our ``Symbols`` file: ``` (cells 1 1 (1 2 3)) ``` As soon as we save it, the drawing is visible. Now we can play with it, add nested lists or change the numbers - the lower drawing will update as soon as we save the upper one. ![nestedlist.gif](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287585392/Myh3jiMOI.gif) ------------------- Of course we can also draw single cell. The function expects again two positioning arguments, followed by the CAR and CDR value: ![pic5.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287593044/ysLlTDgrF.png) ---------------------- ### Visualizing Lisp-functions But we can even do more: Every Lisp-function is a symbol, which means that they are internally represented in cells. For example, the ``curry`` function with ``(cells 1 1 curry)``: ![pic6.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287600996/QeJlRZKF9.png) *Note that this only works for the functions defined in PicoLisp (not machine code) - i. e. all functions defined on the Lisp level as list expressions. -------------------- ### Visualizing classes and objects Just as functions are symbols, so are classes and objects. To highlight this, we can import the [shape.l file](https://gitlab.com/picolisp-blog/web-applications/-/blob/main/docs/shape.l) from the [Object-Oriented Programming tutorial](https://picolisp-blog.hashnode.dev/picolisp-explored-object-oriented-programming-part-1) to the REPL. So, open the REPL first and load the file: ``` $ pil + : (load "shape.l") -> move> : (vi "Symbols") ``` *It is recommended to not to load``shape.l`` inside the ``Symbols`` file, in order to avoid name conflicts with the Vip namespace.* We can visualize the ``+Rectangle`` class with ``(cells 1 1 +Rectangle)``: ![pic7.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287611611/B9OdrthP2.png) And of course we can also show a rectangle object, or rather its properties as list with ``(getl )``: ![pic8.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287618426/bq2EwplQm.png) ------------------- ### Further shapes If you check ``draw.l``, you will see that there are some further shapes available, like boxes and arrows. These can be used to draw simple graphs. Below you can find the quite self-explanatory code for the PicoLisp system graphic below: ``` # VIP @lib/vip/draw.l (box 4 2 75 37 '("base") (label 2 1 "Base System") (box 32 2 11 4 "Cell") (box 15 11 11 4 "Number") (box 49 11 11 4 "Pair") (box 32 21 11 4 "Symbol") (box 54 21 11 4 "List") (box 2 21 11 4 "Short") (box 15 21 11 4 "Bignum") (box 18 31 11 4 "Intern") (box 32 31 12 4 "Transient") (box 47 31 11 4 "Extern") ) (arrow "Number" "Cell") (arrow "Pair" "Cell") (arrow "Symbol" "Cell") (arrow "List" "Pair") (arrow "Short" "Number") (arrow "Bignum" "Number") (arrow "Transient" "Symbol") (arrow "Intern" "Symbol") (arrow "Extern" "Symbol") (box 6 41 15 3 '("http") (label 2 1 "HTTP") ) (box 24 41 15 3 '("form") (label 2 1 "Form GUI") ) ``` ![pic9.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1638287628784/LbBdEik1h.png) The source code can be downloaded [here](https://gitlab.com/picolisp-blog/single-plage-scripts/-/blob/main/vip/Layers). --------------- In the next post, we will see how Vip can support the development and debugging process. --------------- # Sources https://picolisp.com/wiki/?vip