In JoPPS-Script variables are declared implicitly; storage space is dynamically allocated the first time a variable is used.
There are no real datatypes in JoPPS-Script; a variable can hold any type of fundamental data:
numeric (integer, floating points, boolean) , alphanumeric (string) and even represent instances of objects. (IDispatch or JoPPS-Script objects)
JoPPS-Script assigns a subtype to each variable during script execution. This subtype can change dynamically each time a new value is assigned to the variable:
a := 10; /* variable a is of type numeric */
a := "JoPPS"; /* variable a is of type string */
Although variables can contain any type of data it will often be required to check for the type of data that is stored in a variable to ensure proper script execution.
Datatypes are implied by the use of variables in expressions or by passing variables as parameters to JoPPS-Script functions.
We can divide these variable types into 4 categories:
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Variable
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type
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1 holds a numeric value
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floating point, integer, boolean (B-type), date-time value
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D-type
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2 holds a alphanumeric value
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string or character value
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S-type
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3 holds an object instance
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object instance
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O-type
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4 holds an IDispatch instance
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IDispatch object instance
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I-type
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We can verify the type of a variable using the following functions :
IF IsNumber(a) THEN OutputMsg('Is a number');
IF IsString(a) THEN OutputMsg('Is a string');
IF IsObject(a) THEN OutputMsg('Is an object');
IF IsIDispatch(a) THEN OutputMsg('Is an IDispatch instance');
/*for objects we can test for a NILL value..*/
IF IsObject(a) && IsNill(a) THEN OutputMsg('The object is NILL');
String values (S-type) are always between single (') or double (") quotes.
Boolean values (B-type) can be represented using D-type variables:
a := 10; /* <> 0 = true */
IF a THEN OutputMsg("a is TRUE") ELSE OutputMsg("a is FALSE");
a := 0; /* = 0 = false */
IF a THEN OutputMsg("a is TRUE") ELSE OutputMsg("a is FALSE");
The language constants TRUE (=1) and FALSE (=0) can be used instead of 0 and <> 0 to represent the boolean values true and false.
a := TRUE;
IF a THEN OutputMsg("a is TRUE") ELSE OutputMsg("a is FALSE");
a := FALSE;
IF a THEN OutputMsg("a is TRUE") ELSE OutputMsg("a is FALSE");
Note that the language constant TRUE only represents the value 1, this is not the same as "TRUE" which is actually not zero (<> 0).
A variable can be deallocated (freed) by means of the Kill function.
Kill("a"); /* the argument is the name of the variable to free */
At the moment JoPPS-Script has no array type.
Variable naming rules:
- A variable name must begin with an alphabetic character or underscore ("_"). The remainder of the name may contain any alphanumeric characters including underscores.
- The length of the variable is not limited but should be kept as short as possible to improve readability.
- Periods may not be embeded in a variable name.
- A variable name must be unique.
- Variable names are not case-sensitive. (as JoPPS-Script is not case-sensitive)
Variable assignments:
To assign a value to a variable use the assignment operator (e.g. := ) in the format <variable> := <valuegd>.
a := 10;
b := "JoPPS is great";
c := TRUE;
e := d := 5.5;
IF (f := (a + d)) THEN OutputMsg(NumToStr(f));
g := Strings.Create();