Expressions

Using the Symbol Editor > Using More Features of the Symbol Editor > Expressions

Expressions

Expressions are used to customize the format and value of a parameter. For example, you can use an expression to do the following to an object:

Blink in two different colors.
Display the date in a specific format.
Join the value of two expressions.
Return the square root of a parameter.

An expression can be set on any attribute contained in a symbol. To use an expression on an object, do the following:

Open the symbol you made in Creating a Rotation Interactor for Multiple Objects.
Select the Text object.
Click the Text tab in the Styling Customizer.
Right-click the Label field. A shortcut menu appears.
Click Enter an Expression.
Delete the contents of the Label field. It is changed into a drop down list.
Click the down arrow on the right of the Label field. The list of expressions appears.
Select the @rotationValue expression.
Fill in the expression as follows, rotationValue(0,360,@rotate,0,360).
Test this symbol by clicking the Preview button.

As you rotate the mouse over the symbol, the Text label is updated to show the angle of rotation.

Expressions can combine other expressions, model attributes and string literals. For example, the following expression prints the integer value of a parameter in a string.

concat("the rotation value is ", rotationValue(0,360,@rotate,0,360), ".")

Note

When creating expressions, always select values from the list, do not type the parameter name or expression by hand.

Possible expressions are listed in Table 2.2.

Table 2.2 Symbol Editor Expressions

Name	Description	Example
`parameter`	Any parameter in the symbol	`@rotate`
`rotationValue`	Calculates the rotation angle	`rotationValue(@rotate)`
`int`	Casts the parameter to an `Integer`	`int(@rotate&100)`
`decimalFormat`	Reformats a parameter value. See `java.text.DecimalFormat` for more information.	`decimalFormat("#.#", pi) -> 3.1`
`childrenCount`	Returns the number of child objects below this object	`childrenCount()=0`
`simpleDateFormat`	Formats a `date`. See `java.text.SimpleDateFormat` for more information.	`simpleDateFormat("MM/dd/yyyy",@date)` This will give: 10/01/2001
`long`	Casts to a `long` value	`long(@val1+@val2)`
`double`	Casts to a `double` value	`double(@value*3)`
`messageFormat`	Formats different strings to a specific message format. See `java.text.MessageFormat` for more information.	`messageFormat('{0}: {1,number,#.##}','result',44.2874)` This will give: 44.28"
`blinkingColor`	Specifies 2 different colors to alternate for a graphic object	`blinkingColor(green,yellow)`
`concat`	Concatenation for String parameters	`concat("result is:",@result)`
`float`	Casts parameter to a float value	`float(cos(@value))`
`abs`	Absolute value of the parameter	See `java.lang.Math`
`acos`	Returns the arc cosine of an angle, in the range of 0.0 through pi	See `java.lang.Math`
`asin`	Returns the arc sine of an angle, in the range of -pi/2 through pi/2	See `java.lang.Math`
`atan`	Returns the arc tangent of an angle, in the range of -pi/2 through pi/2	See `java.lang.Math`
`ceil`	Returns the smallest (closest to negative infinity) double value that is not less than the argument and is equal to a mathematical integer	See `java.lang.Math`
`tan`	Returns the trigonometric tangent of an angle	See `java.lang.Math`
`cos`	Returns the trigonometric cosine of an angle. Special cases:	See `java.lang.Math`
`exp`	Returns Euler's number e raised to the power of a double value	See `java.lang.Math`
`floor`	Returns the largest (closest to positive infinity) double value that is not greater than the argument and is equal to a mathematical integer	See `java.lang.Math`
`log`	Returns the natural logarithm (base e) of a double value	See `java.lang.Math`
`rint`	Returns the double value that is closest in value to the argument and is equal to a mathematical integer	See `java.lang.Math`
`sin`	Returns the trigonometric sine of an angle	See `java.lang.Math`
`sqrt`	Returns the correctly rounded positive square root of a double value	See `java.lang.Math`
`tan`	Returns the trigonometric tangent of an angle	See `java.lang.Math`

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