pylogram
========

A very simple declarative linear equation solver and drawing package. A reimplementation of Mark Dominus' linogram, described in:

 Several blog posts (reverse order) at http://blog.plover.com/linogram/
 Source code on github at https://github.com/mjdominus/Linogram
 Originally developed in the book Higher Order Perl (http://hop.perl.plover.com/book/)

In most programming languages you can't assign to expressions: 2+3=x doesn't work. But if x is a pylogram Var x becomes equal to 2+3, unless that conflicts with a previous expression, in which case a Contradiction exception is thrown.

An example of use to solve a set of linear equations would be:
 
    from pylogram import constrain, default_vars as vars
    constrain(   vars.a + vars.b   == 2  ,
               2*vars.a + vars.b/3 == -7 )
    print( "a , b =", vars.a, ",", vars.b )
    
Which gives output:

 >> -23/5 , 33/5

An example of geometric drawing would be:

    from pylogram_draw import *
    
    class Lollypop(Primitive):
        def __init__(self):
            self.stick = Line('stick')
            self.circ = Circle('ball')
            self.circ.bottom = self.stick.pt1
            self.stick.pt1.x = self.stick.pt2.x
            line_height = self.stick.pt2.y - self.stick.pt1.y
            line_height [:]= self.circ.d * 2
            self.bottom = self.stick.pt2
            self.height = line_height + self.circ.d
    
    lollypop = Lollypop()
    lollypop.bottom = Point(1,0)
    lollypop.height = 6
    
    assert lollypop.circ.c == Point(1,-5)
    lollypop.sim_draw()

Which gives output:
    
 >> Drawing circle about 1,-5 with radius
 >> Drawing line from 1,-4 to 1,0

For a linear equation from a riddle 1800 years old, see example_diophantus.py
For a slightly longer drawing example including displaying to screen, see example_lollypop.py