Tyl Programming Language
▶ BOOLEANS
Boolean variable has only two optional values: TRUE, FALSE.
To declare a boolean variable, write:
``` is_solid \t is_liquid \f ```
Tyl symbolizer will replace '\t' with '' (the TRUE symbol), and '\f' with '' (the FALSE symbol):
``` is_solid ｔ is_liquid ｆ ```
If you want to change the value of a boolean variable to its opposite value, use the `not` system function:
``` is_solid ｔ is_liquid not is_solid ```
In line: '`is_liquid not is_solid`', `is_liquid` variable gets the result of the negation of `is_solid` variable.

There are some boolean operators that can be applied to boolean variables. AND operation will yield the result: TRUE, if both variables are TRUE.

AND operation:
``` is_solid ｔ is_blue ｔ is_solid_and_blue is_solid * is_blue ```
The multiply operator: '*', is used as the AND operator for boolean variables.

OR operation will yield the result: TRUE, if at least one variable is TRUE.

OR operation:
``` is_solid ｔ is_blue ｆ is_solid_or_blue is_solid + is_blue ```
The plus operator: '+', is used as the OR operator for boolean variables.

In Tyl we use also the divide operator: '/', to make a special boolean operation: AND_NOT.

The operation: `A AND_NOT B`:
``` is_solid ｔ is_blue ｆ is_solid_but_not_blue is_solid / is_blue ```

Here's Move Colors program:
``` is_red ｔ is_green ｆ is_blue ｆ move_left »  temp is_red  is_red is_green  is_green is_blue  is_blue temp move_right »  temp is_blue  is_blue is_green  is_green is_red  is_red temp get_color »  is_red ?   'RED'   ╌   is_green ?    'GREEN'    ╌    is_blue ? 'BLUE'   ᐤ  ᐤ main »  print get_color  move_right  print get_color  move_right  print get_color  move_left  print get_color  move_left  print get_color ```
RED
GREEN
BLUE
GREEN
RED