Operators and Expressions¶

Operators¶

Operators are the commands which tells the TROIA interpreter to do some mathematical,relational and logical operations using their operands.

Arithmetic Operators¶

Operator	Meaning
+	add, string concatenate
-	subtract
*	multiply
/	divide
%	module
^	power

Relational Operators¶

Operator	Meaning
==	is equal to
!=	is not equal to
>	is greater than
>=	is greater than or equal to
<	is less than
<=	is less than or equal to

Logical Operators¶

In TROIA codes, there are two set of logical operators. The first set is about TROIA expressions that is used on if, where, loop etc. conditions.

Operator	Meaning
!	not
&&	and
\|\|	or

Elements of second logical operator set are OR, AND and NOT. This operators are not elements of TROIA language, they are just used in SQL commands that written inside TROIA codes. This operators are not supported on if, where or loop statement conditions etc. Although these are not used as logical operators, it is not recommended to define variables with this names.

Assignment¶

There are two assignment methods in TROIA. First method is using MOVE command, which does not support expressions for source value.

MOVE 'Hello World' TO STRINGVAR1;
MOVE STRINGVAR1 TO STRINGVAR2;
MOVE 3 TO INTEGERVAR1;

MOVE 3 + 1 TO INTEGERVAR1;     /* not valid, no expression support*/
MOVE THIS.F1() TO INTEGERVAR1; /* not valid, no expression support*/

Second assignment method is using = operator. This method also supports expressions in right hand side.

STRINGVAR1 = 'Hello World';
STRINGVAR1 = STRINGVAR1 + 'Hello World';
INTEGERVAR1 = 3 * (5 + INTEGERVAR1);

INTEGERVAR1 = ABS(5 - 10);

Expressions¶

Simply an expression is right hand side of = operator and it can be consisted of even a single variable or combinations of multiple operators and function calls. Expressions are not for only using assignment operations. They are also used on function calls as a parameter or on RETURN command when you need to return result of an expression. Here is a simple list of mostly used commands that support expressions, details of this commands discussed in next sections.

on function call as function parameter
on IF command condition
on WHILE command condition
on LOOP command condition
on RETURN command

. . .
INTEGERVAR1 = THIS.F1(4+INTEGERVAR2, 'parameter value', P3);

RETURN INTEGERVAR1 + 5;

THIS Keyword¶

One of the most used elements of expressions is function call. In TROIA language, specifying instance name of class/dialog is a must. THIS keyword is used for indicating same instance. In other words, if you want to call another method of the class/dialog in its method you must use THIS keyword.

A function calls which does not include instance name is considered as a system function. System functions are predefined functions to ease some mostly used operations like mathematical operations, string operations etc.

Most used system functions will be discussed in related sections, for all system functions please see TROIA Help.

CUSTREC.CALCULATE(P1);   /* call CALCULATE method of CUSTREC object */
THIS.SEARCH(P1);         /* call SEARCH method of same class/dialog */
RESULT = ABS(5 - 10);    /* call a system function                  */

Some facts about calling functions/methods¶

Sending more parameters than called method requests is not considered a TROIA programming error. System just ignores extra parameters. If you send less parameters, system assigns default values to missing parameters.

If you want to pass default values for parameters except last parameter, you must leave parameter empty.

RESULT = MYINS1.CALCULATE(P1,,,P4);

/* send default values to P2 and P3 */

In system function calls, sending less or more parameters is not recommended, if it is not documented in function help.

Type Conversion and Casting¶

In TROIA, simple typed variables are casted automatically, so there is not an extra operator or method for type casting. For example, you can directly assign an double to string, or a string to a double symbol. If system fails to convert types assigns default value of destination symbol.

Type casting is not supported for complex types such as TABLE, VECTOR or class instance. Actually, assigning this complex types is not a usual method, because TROIA has special commands for data transfer between complex types, especially for tables.

OBJECT:
        STRING SOURCESTR,
        DOUBLE DESTDOUBLE,
        INTEGER DESTINT,
        DATE DESTDATE,
        LONG DESTLONG,
        DATETIME DESTDATETIME;

        SOURCESTR = '6.0';

        DESTDOUBLE = SOURCESTR;   /* double is now 6.0 */
        DESTINT = DESTDOUBLE;     /* integet is now 6  */

        SOURCESTR = '25.11.1984';

        DESTDATE = SOURCESTR;     /* date is now 25.11.1984 */
        DESTLONG = DESTDATE;      /* long is now long value of given date */
        DESTDATETIME = DESTLONG;  /* datetime is now 25.11.1984 00:00:00 */
        SOURCESTR = DESTDATETIME; /* string is now '25.11.1984 00:00:00' */

Here is as simple table that shows casting operation between source and destination simple types. In this table x-axis shows destination variable type and y-axis shows source variable type.This conversion table is valid for both of MOVE and assignment operator.

	DESTINATION TYPE
	STRING	INTEGER	LONG	DECIMAL	DATE	DATETIME
STRING		parse,if fails-> 0	parse,if fails-> 0	parse,use . as sep. if fails-> 0.0	parse, if fails set NULLDATE(1)	parse, if fails set NULLDATE(2)
INTEGER	convert to string		no extra operation, just assign	assign int val, use .0 as fractional part	add value as ms. to 01.01.1970	add value as ms. to 01.01.1970 00:00:00
LONG	convert to string	assign, if exceeds set->0 (??)		assign long val use .0 as fractional part	add value as ms. to 01.01.1970	add value as ms. to 01.01.1970 00:00:00
DECIMAL	convert to string	assign only whole part	assign only whole part		add whole part as ms. to 01.01.1970	add whole part as ms. 01.01.1970 00:00:00
DATE	convert to string with dd.MM.YYYY pattern	assign long value from 01.01.1970 00:00:00	assign long value from 01.01.1970 00:00:00	not allowed assigns 0		uses 00:00:00 as hour part
DATETIME	convert to string with dd.MM.YYYY HH:mm:ss	assign long value from 01.01.1970 00:00:00	assign long value from 01.01.1970 00:00:00	not allowed assigns 0	assign only date part

(?) NULLDATE : .

(??) Limits of Integer : .

Exercise 1: Integer Arithmetic¶

Here is a simple arithmetic example. Please think on this example and try to find why DECIMALVAR1 and DECIMALVAR2 values are different even if divide operation is same.

OBJECT:
        INTEGER INTEGERVAR1,
        DECIMAL DECIMALVAR1,
        DECIMAL DECIMALVAR2;

INTEGERVAR1 = 3;
INTEGERVAR1 = INTEGERVAR1 * (1 + 2);
INTEGERVAR1 = INTEGERVAR1 ^ 2 + 4;
INTEGERVAR1 = INTEGERVAR1 % 60;

DECIMALVAR1 = INTEGERVAR1 / 6.0;
DECIMALVAR2 = INTEGERVAR1 / 6;