5.2. Using Variables
Syntax:
VariableNameExample:
genius> e = 2.71828182846
To evaluate a variable by itself, just enter the name of the variable. This will return the value of the variable. You can use a variable anywhere you would normally use a number or string. In addition, variables are necessary when defining functions that take arguments (see Section 5.3.1).
 | Using Tab completion |
|---|---|
You can use Tab completion to get Genius to complete variable names for you. Try typing the first few letters of the name and pressing Tab. |
 | Variable names are case sensitive |
|---|---|
The names of variables are case sensitive. That means that variables named hello, HELLO and Hello are all different variables. |
5.2.1. Setting Variables
Syntax:
<identifier> = <value> <identifier> := <value>Example:
x = 3 x := 3
To assign to a variable, use the = or := operators. These operators set the value of the variable and return the number you set, so you can do things like
a = b = 5
The = and := operators can both be used to set variables. The difference between them is that the := operator always acts as an assignment operator, whereas the = operator may be interpreted as testing for equality when used in a context where a Boolean expression is expected.
5.2.2. Global variables
Sometimes you'd like to set a global variable from inside a function. For this, use the set function. Passing a string or a quoted identifier to this function sets the variable globally. For example, to set a to the value 3 you could call:
set(`a,3)or:
set("a",3)
Like most programming languages, Genius has two different types of variables: local (a variable set inside a function will not exist outside the function) and global (doesn't matter where you set them).
5.2.3. Built-in variables
GEL has a number of built-in ‘variables’, such as e. These are widely used constants with a preset value, and they cannot be assigned new values. There are a number of other built-in variables, such as pi and GoldenRatio. See Section 10.4 for a full list.
5.2.4. Previous result variable
The Ans and ans variables can be used to get the result of the last expression. For example, if you had performed some calculation, to add 389 to the result you could do:
Ans+389