Comparison with other programs

There may be other programs in this field, for example Macaulay2, but I have not evaluated it, so I can't really comment about alternatives.

Evaluate Program

I am working on this program to produce graphs and tables for this site, also to analyse and compare different algebras, it is not yet in a state where it would be useful for others so I have not yet made any code available.

I don't even have a name for this program (and its associated language) yet, I have used 'evaluate' so far but I might call it EuclieanSpace after this site?

The program will evaluate, simplify, plot and do other operations on mathematical expressions. The program is mostly intended to operate with multivectors and matrices but it can operate with scalars (real numbers) and integers.

As an example of where I have used this program to plot graphs see this page.

As an example of where I have used this program to compare the algebraic properties of different algebras see this page.

The program is driven by an XML configuration file which is like a source code language. I have designed this 'language' to be structured, as far as possible, similar to the Java language. So this program can be thought of as a specialist mathematical compiler. Since the configuration file is based on XML it is tree structured consisting of different types of node which I have listed below. If you would prefer to work in terms of a text based source code there is a semantic analyser available which will convert from a text representation to the XML tree structured representation(see the XES program here.).

Some of the main differences between this language and Java are:

program design choice	Java	Evaluate
built-in types	int,long,byte,float,double,boolean,String other types can be built by writing classes	int,scalar,multivector,matrix.
operations on numerical types	+ - * / and bitwise (&,| and ^ )	+,geometric, inner and outer products.
maths functions	Math class library	inverse,conjugate,reversal
output functions	extensive built-in class library (mostly low level).	outputTable, outputFormula, outputSvg and outputXml.
variable definition	numeric variable types have name, type and visibility only. These cannot be changed when the program is running(static typing).	variable types have lots of parameters like dimension, which dimensions square to -ve. attributes of elements, sub-algebras, etc. These cannot be changed when the program is running(static typing).
variables	store numeric values (int or float)	can store numeric values or symbolic formula (such as: a*2+b).

The program is written in java although perhaps on day it could be written in its own language.

Configuration File (Source Code) Definition

Nodes

The program holds the mathematical expressions and all its data in a tree structure which it can read and write to an xml file structure.

The data structure consists of a tree with the following nodes:

class

Groups together related variables and procedures.

multiOp

This represents operations like +,*,-,/,and,or

can contain 2 or more operands

• op1
• op2
• op3...

uniOp

This represents operations like not,-,invert,conj

• op1

variable

Holds an instance of a variable. Just before runtime this is linked to varDef node

• varDef

constant

holds scalar number or array of numbers to represent the value of an integer, scalar, multivector or matrix.

• array of scalars
• mathType

varDef

This holds the name, visibility and mathType of the variable being defined. Before runtime variables are linked to this and it is linked to the appropriate mathType.

mathType

Defines;

• name
• type; int, scalar, multivec, matrix
• number of dimensions.
• square to -ve or not for each dimension.
• multiplication table for; geometric, inner and outer products.
• inverse table

array

Defines array of a given variable

call

calls a given procedure. Before runtime it is linked to procedure definition.

procedure

Defines a procedure. Before runtime calls that us this are linked.

return

Element of procedure which can optionally be used to return a value if required.

assignment

Assigns a value to a variable. contains;

• variable
• expression; multiop or unaryop or call or variable or constant

simultaneous

Contains multiple condition nodes, solved mathematically not procedurally.

condition

Has two expression nodes and a relation value.

if

contains a condition node and a group or any other node which is executed if condition is true.

group

groups together other nodes so that a sequence can be represented as one node.

loop

Represents functionality of 'for', 'do' or 'while'.

comment

Text to help readability

Program Operation

The following links are setup just before runtime:

• variable -> varDef
• varDef -> mathtype
• call -> procedure

Library Items

scalar elements are represented by vaiable-element pair.

outputTable

child nodes;

• varDef - variable definition node

This can allow the program to compare the multiplication tables (the essence of an algebra - for more information about these "Cayley" tables see this page) of different algebras.

The program generates the multiplication (Caley) table for a given algebra and can then do things like checking for commutivity and associativity, it does this by a sort of brute force method of trying all the possible combinations, if you know a more elegant mathematical method please let me know.

I have not properly validated this program so all these results should be treated as tentative. It is very difficult, take the associativity test, the progam tests (a* b)*c and a*(b * c) where we test every combination of a,b and c each of which, in the case of a clifford algebra based on 4D vectors, can have a value between 0 and 7 giving 8*8*8=512 combinations. If any of these are not associative then this is reported and its easy to check manually, but if the program goes through all combinations and finds the table associative, but how do I confirm that one of these combinations is not wrong?

Also the program only checks the commutivity and associativity of the basis values on their own, if does not check the commutivity and associativity of linear sums of these which make up a complete multivector.

I would like to extend this program to directly compare two multiplication tables. This is quite difficult because we not only need to compare the tables as they stand but also all combinations of swapping and inverting terms.

outputFormula

child nodes;

outputSvc

child nodes:

• input = varDef node - indicates variable,element pair and range for bottom axis.
• output = function heirachy of nodes (containing input varDef node since output will be a function of this).

parameters:

• axis with scale and coordinates

Relationship between x value and pixel horizontal offset

i = pixel horizontal offset

i = C + x*(xAxisPos1 -xAxisPos1)

x = (i-xAxisPos1)/(xAxisPos1 -xAxisPos1)

LeftLimit -> i=0 x = (-xAxisPos1)/(xAxisPos1 -xAxisPos1)

RightLimit -> i=gridWidth x = (gridWidth-xAxisPos1)/(xAxisPos1 -xAxisPos1)

outputXml

child nodes;

• for,element(s) - indicates variable,element pair and range for bottom axis.
• variable(s),element(s)