Conditionals

Conditionals are used at very points in the Slow Glass scripting language, for example with the when trigger, the if command and the until / while loops. In accordance with the design principles the conditional evaluation method is very simple.

Single Word Conditions

If the condition consists of a single word then it will be treated as a string. The following string values are assumed to be false:

false, 0, no, 0.0, NONE

Every other string is assumed to be true.

Whilst this might appear rather limited it does tie in nicely with the built-in variables, so you can do things like:

if $MORNING

And things will work as you expect.

Three Word Conditions

If the condition contains three words then we assume that the first and third are values and the second word is a comparison operator. The following comparison oerators are supported:

is, equals, =, ==, !=, <>, >, >=, <, <=

The two values are treated as strings and evaluated against the comparison using JavaScript evaluation. It most cases you don’t need to worry about data types it should just work as you expect, strings of digits are compared as numbers, strings are compared alphabetically and so on.

Negating the condition

You can prefix one or three word conditions with the word *not*. This simply inverts the result of the comparison.

Expressions

Anything that is enclosed in round brackets is assumed to an expression and is replaced by the result of evaluating that expression. Note that Slow Glass variables are expanded BEFORE expression evaluation.

Note the expressions can appear anywhere, not just in conditional commands, so the following is perfectly legal:

move sprite_name to (12 * 12) (4 + 4)

More usefully, since variables are expanded before expressions you can do things like:

darken sprite-name by ($SUNANGLE * 0.5)

You can also nest brackets to any required depth and they will treated correctly within an expression.

Simple Evaluator

Slow Glass provides two options for evaluating expressions. The default is known as the “simple” evaluator, although it should be sufficient for most needs. All the standard operator symbols are supported, including ! and ^ for factorial and power. Brackets can be nested to any depth. ‘Pi’ and ‘e’ are replace by their respective values. The following functions are supported:

• sin cos tan asin acos atan sinh cosh tanh asinh acosh atanh - trigonmetric, angles in degrees
• Mod log ln - modulus & logarithms (note capitals)

Full documentation for this expression evaluator can be found here.

Advanced Evaluator

If more sophistication is required SlowGlass can be configured to use an advanced evaluator that is fully documented here. It supports many more operators, conditionals, different bases, its own system of variables and much more.