Expr2Graph

A Converter from Expression to Graph(dot)

Compile

1. build using Stack

   stack build

2. run with Stack

   stack run

3. test with Stack

   stack test

Usage

An expression in each line, whose syntax is as below.

Syntax

We use syntax based on (Actually the same as by now) this CodeWars Kata which meas we Parse an function defined as below.

function   ::= '[' arg-list ']' expression

arg-list   ::= /* nothing */
                 | variable arg-list

expression ::= term
                 | expression '+' term
                 | expression '-' term

term       ::= factor
                 | term '*' factor
                 | term '/' factor

factor     ::= number
                 | variable
                 | '(' expression ')'

For example these functions below are OK

[ a b ] a*a + b*b
[ first second ] (first + second) / 2
[a b c]a*a+b*b+(a+b)*(a+c)/2

Output

NOTICE: This program DOES NOT generate any image format such as svg or jpeg but the content of an dot file, which can convert to an image file using Graphviz.

So you can use command like this to generate an image

echo "[a b] (a+b)/2" | stack run | dot -Tsvg > graph.svg

BTW this result is as below

Elements

Symbol	Meaning
Circle	Operator such as +,-,*,/
Box	An Immediately number(only Integers for now)
Box3D	The Index(beginning with 0) of an Argument

Known Bugs

• When combining sub-trees, there are still some duplicate errors in graph ([a b] a*a + a*b + a*b + b*b as below)

  

TODO-List

• More operator such as ^
• Some new feature like let...in...
• Named function
• Recursion support