Chapter 5. GEL Basics

Table of Contents

Using Variables
Setting Variables
Built-in Variables
Previous Result Variable
Using Functions
Defining Functions
Variable Argument Lists
Passing Functions to Functions
Operations on Functions
Modular Evaluation
List of GEL Operators

GEL stands for Genius Extension Language. It is the language you use to write programs in Genius. A program in GEL is simply an expression that evaluates to a number, a matrix, or another object in GEL. Genius Mathematics Tool can be used as a simple calculator, or as a powerful theoretical research tool. The syntax is meant to have as shallow of a learning curve as possible, especially for use as a calculator.


Values in GEL can be numbers, Booleans, or strings. GEL also treats matrices as values. Values can be used in calculations, assigned to variables and returned from functions, among other uses.


Integers are the first type of number in GEL. Integers are written in the normal way.


Hexadecimal and octal numbers can be written using C notation. For example:


Or you can type numbers in an arbitrary base using <base>\<number>. Digits higher than 10 use letters in a similar way to hexadecimal. For example, a number in base 23 could be written:


The second type of GEL number is rationals. Rationals are simply achieved by dividing two integers. So one could write:


to get three quarters. Rationals also accept mixed fraction notation. So in order to get one and three tenths you could write:

1 3/10

The next type of number is floating point. These are entered in a similar fashion to C notation. You can use E, e or @ as the exponent delimiter. Note that using the exponent delimiter gives a float even if there is no decimal point in the number. Examples:


When Genius prints a floating point number it will always append a .0 even if the number is whole. This is to indicate that floating point numbers are taken as imprecise quantities. When a number is written in the scientific notation, it is always a floating point number and thus Genius does not print the .0.

The final type of number in GEL is the complex numbers. You can enter a complex number as a sum of real and imaginary parts. To add an imaginary part, append an i. Here are examples of entering complex numbers:



When entering imaginary numbers, a number must be in front of the i. If you use i by itself, Genius will interpret this as referring to the variable i. If you need to refer to i by itself, use 1i instead.

In order to use mixed fraction notation with imaginary numbers you must have the mixed fraction in parentheses. (i.e., (1 2/5)i)


Genius also supports native Boolean values. The two Boolean constants are defined as true and false; these identifiers can be used like any other variable. You can also use the identifiers True, TRUE, False and FALSE as aliases for the above.

At any place where a Boolean expression is expected, you can use a Boolean value or any expression that produces either a number or a Boolean. If Genius needs to evaluate a number as a Boolean it will interpret 0 as false and any other number as true.

In addition, you can do arithmetic with Boolean values. For example:

( (1 + true) - false ) * true

is the same as:

( (true or true) or not false ) and true

Only addition, subtraction and multiplication are supported. If you mix numbers with Booleans in an expression then the numbers are converted to Booleans as described above. This means that, for example:

1 == true

always evaluates to true since 1 will be converted to true before being compared to true.


Like numbers and Booleans, strings in GEL can be stored as values inside variables and passed to functions. You can also concatenate a string with another value using the plus operator. For example:

a=2+3;"The result is: "+a

will create the string:

The result is: 5

You can also use C-like escape sequences such as \n,\t,\b,\a and \r. To get a \ or " into the string you can quote it with a \. For example:

"Slash: \\ Quotes: \" Tabs: \t1\t2\t3"

will make a string:

Slash: \ Quotes: " Tabs: 	1	2	3

Do note however that when a string is returned from a function, escapes are quoted, so that the output can be used as input. If you wish to print the string as it is (without escapes), use the print or printn functions.

In addition, you can use the library function string to convert anything to a string. For example:


will return


Strings can also be compared with == (equal), != (not equal) and <=> (comparison) operators


There is a special value called null. No operations can be performed on it, and nothing is printed when it is returned. Therefore, null is useful when you do not want output from an expression. The value null can be obtained as an expression when you type ., the constant null or nothing. By nothing we mean that if you end an expression with a separator ;, it is equivalent to ending it with a separator followed by a null.



Some functions return null when no value can be returned or an error happened. Also null is used as an empty vector or matrix, or an empty reference.