Data Types

Variables come in different types, playing by different rules.

Booleans (True or False values)

A boolean value is true or false.

is_on_fire = true or weapon_held = false.

The not or ! operator inverts a boolean between true and false. not true is false. is_toggled = not is_toggled would switch between true and false.

You can combine booleans, described below.

Variable Comparison

You can compare any variables for equality, which returns a boolean value.

• == means "are equal?" 2 == 3 is false.
• != means "are not equal?" 2 != 3 is true. (Remember ! means the same as not, so != means 'not equal')

People sometimes compare booleans with true or false. That's silly. is_active == true means the same thing as is_active. is_active == false means the same as not is_active.

Numbers have more operators, >, >=, <, and <=, described below.

if statements use variable comparison extensively.

Logical Operators

You can combine booleans with logical operators and and or.

can_use_fireball = fireball_ready == state_cat != SC_HITSTUN
bomb_should_explode = fuse_timer <= 0 or should_die

You can technically use 0 and 1 as false and true respectively. Don't. It makes the intention of the code much less clear, because the reader must guess whether the value is a boolean or number. If a value is true or false, use true and false.

Some misconceptions. (opens new window)

Reals (Numbers)

Most variables hold numbers, such as speed or percent or x position.

You can also compare numbers by their relative size.

• > - 'is greater than?'
• >= - 'is greater than or equal to?
• < - 'is less than?',
• <= - 'is less than or equal to?'

Numbers can use math operators +, -, * and /.

When increasing or decreasing a variable, you can use +=, -=, *= and /= as a shortcut. x += 1 increases x 1, the same as x = x+1.

my_var++ or my_var-- are shorthand for my_var+=1 and my_var-=1.

Integers

All numbers are reals. Integers are a subset of reals with no decimal value. 1, -100, 4140 are integers, while 2.5 is not.

Rivals expects some variables to be integers, such as x and y positions. If you ever need to convert a real to an integer, you can use rounding functions (opens new window) like round, floor and ceil.

GML Reals Official docs (opens new window)

Strings (text)

Strings are text. Rivals doesn't need a lot of text processing, but they're used when using print or displaying text as part of a HUD.

String value are anything between quotes, either single '...' or double "...".

You can add strings together with +. "a" + "b" == "ab".

Official docs (opens new window)