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BSL:Variables: Difference between revisions
updated general notions
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The usual thing to do in this situation is to store the needed data in a '''variable''': an elementary data container. | The usual thing to do in this situation is to store the needed data in a '''variable''': an elementary data container. | ||
==General notions== | |||
===Type and value=== | |||
A variable (data container) has three important attributes: the ''name'', the ''type'' and the ''value''. | |||
An easy way to get the type and value of an existing BSL variable is to enter its name at the console in [[Developer Mode]]: you typically get console output like "bool: 1" or "int32: 42" or "float: 3.14" or "string: hello" | The ''value'' or the variable is just the contents it currently stores. It can be read and written. | ||
==Declaration== | |||
Also, a given variable can store only a specific ''type'' of data (floating-point number or integer or text string or boolean), and that is what we call the variable's type. | |||
==Assignment== | |||
Finally, the ''name'' of a variable is a unique text string that is used to identify the data container within the script. Like [[BSL:Functions|function]] names, variable names are case-sensitive (NOTE: [[BSL:Preset|preset]] variables and functions are all lower-case). Valid characters are: ''please fill me in'' | |||
An easy way to get the ''type'' and ''value'' of an existing BSL variable is to enter its ''name'' at the console in [[Developer Mode]]: you typically get console output like "bool: 1" or "int32: 42" or "float: 3.14" or "string: hello" | |||
---- | |||
===Declaration and assignment=== | |||
If you want to use a new variable (data container), you must set it up (''declare'' it) first, with the '''var''' keyword. A declaration statement can look a bit like this: | |||
var int my_superduper_integer; | |||
var bool my_totally_awesome_boolean; | |||
var string my_incredible_text_string; | |||
var float my_cool_floating_point_number; | |||
The first word is the keyword "var", next comes the type (keyword), then the name of the variable. The final ";" is required. The name can be any valid name (i.e., not a keyword and not containing invalid characters) | |||
A declaration is usually seen at "global scope" (i.e., outside all functions). It is recommended to group declarations at the beginning of a BSL file (for readability), but it's not necessary. It is also not necessary (but strongly recommended) to declare a variable ''before'' the context where it is used for the first time. | |||
On some occasions you may want to declare a ''local'' variable (i.e., to embed a declaration statement into a [[BSL:Functions|function]]). This feature will be detailed elsewhere. | |||
---- | |||
===Assignment=== | |||
You can assign a new value to an existing variable with the assignment operator "=". The name of the variable you want to modify is on the left-hand-side (LHS) of the "=", and on the right-hand-side (RHS) you can have any valid [[BSL:Expressions|expression]] that evaluates/converts into the variable's type. | |||
An assignment can be combined with a declaration (see above). That means the variable will have a definite value right after it is created. If you don't specify/define such a starting value, you should not, generally speaking, assume anything about the value. | |||
However, apparently there ''are'' "default" values assigned to every variable even if it hasn't been defined yet. Those values are 0 (i.e., false) for bool, 0 for int and float, and "" (empty string) for string. | |||
---- | |||
===More=== | |||
Later. | |||
---- | |||
---- | |||
==Preset variables== | ==Preset variables== | ||
;All the preset OSL variables are listed here, in alphabetical order. | ;All the preset OSL variables are listed here, in alphabetical order. | ||
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|bool||[[ai2_showactivationpaths]]||0 | |bool||[[ai2_showactivationpaths]]||0 | ||
|shows the initial pathfinding (upon | |shows the initial pathfinding (upon activation) of all AI||OK | ||
|- | |- | ||
|bool||[[ai2_showastar]]||0 | |bool||[[ai2_showastar]]||0 | ||