If Expression


This action is used to check that an expression as either true or false, and you can check any logical expression here as long as it evaluates to one or the other value. For example, any of the following expressions could be used:

x < (room_width / 2)
a == b
++val >= 100

If you flag the "Not" argument, then the above will be negated expressions, for example "==" becomes "not=". Also note that the expression is not limited to numeric values and you can check strings, pointers, resource IDs or anything else that a function can return or use (see the section on data types for more information), but you cannot compare two different data types without getting an error - for example if you try to use a string and an integer in the expression you will get an error. For more information on expressions, see here.

IMPORTANT NOTE: Due to floating point precision issues, checking to see if two values are exactly equal may return false, since one may be exactly 1, while the other may be 1.00000000000001. This can be avoided by using the Decimal to Integer action before checking or using the "greater than (>)" or "less than (<)" expressions.

Note that to add actions into the "if" block, they should be dropped to the side of the action, as shown in the image below:
If Expression Add Actions

These actions will now be run if the "if" evaluates to true, while any actions dropped elsewhere will be performed after the "if" block. Note that you can "stack" expressions in the same action by clicking the plus icon beside the action, and giving another expression to check. This will check if all the expressions given return true in one check and only perform the added action code if they do (see the example given below).

Action Syntax:

If Expression Syntax


Argument Description
Expression The expression to check.
Not Set to check if the expression does not evaluate to true.


If Expression Action Example

The above action block code checks to see if the instance variable "player_score" is greater than 1000 and that the instance variable "player_level" is less than 10. if both checks return true then the action code goes on to assign new values to these variables.