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This is essentially the same as the OGRE expression language, with the following changes:

1. The reference tag $R has been eliminated, with variables and properties generalized to $.
2. The index tag $I has been generalized to include keys to a Map.
   
   

Except for restrictions on the placement of index tags (they must be inside a reference and cannot be nested inside other index tags), all of these are nestable within one another and to an arbitrary depth. Some simpler examples:

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The value returned here would be of type java.lang.Boolean; the value of k would be appended to 'currentValue_' and this string used as the name of another reference which should correspond to a stored numerical value; the value of j would then be compared to it.

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1. all operators and operands must be white-space delimited (but unary -/+ should remain attached to its argument)
2. any of the Java operators except: ternary condition ' ? : ', cast, instanceof, assignment (++ and – - here are merely shorthand for + 1 and - 1, with no side-effecting implied)
3. any of the functions available from java.lang.Math; parameters must be comma-delimited inside the parentheses
4. any numeric operand
5. pi, e
6. true, false

The resulting string is not type-checked, but loose parenthesis matching is enforced (e.g., '( 1 * ( 2 - 3 )' or '( 1 * ( 2 - 3 ) ) )' will be rejected, but '( ) ( 1 * ( 2 - 3 ) )' will be accepted, with the empty parenthesis parentheses simply ingored).

XML Escaped Characters

When coding expressions, the greater-than ('>') and less-than ('<') characters should be escaped to > and <. > and <.

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An example, with output, of expressions, constants and literals, using a for container task:

<ogrescript strict="true">
	<for var="i" from="0" to="10">
	   <echo stdout="true" message="******************** ${i} ********************"/>
		<echo stdout="true" message="the expression value is $E{ 10 * ( ${i} + 1 ) }"/>
		<echo stdout="true" message="the constant value is $C{$E{ 10 * ( ${i} + 1 ) }}"/>
		<echo stdout="true" message="the literal value is '$L{$E{ 10 * ( ${i} + 1 ) }}'"/>
	</for>
	<echo stdout="true" message="********************************************"/>
</ogrescript>

OUTPUT:

******************* 0 *******************
the expression value is 10
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 1 *******************
the expression value is 20
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 2 *******************
the expression value is 30
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 3 *******************
the expression value is 40
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 4 *******************
the expression value is 50
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 5 *******************
the expression value is 60
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 6 *******************
the expression value is 70
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 7 *******************
the expression value is 80
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 8 *******************
the expression value is 90
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 9 *******************
the expression value is 100
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
******************* 10 *******************
the expression value is 110
the constant value is 10
the literal value is '$E{ 10 * ( ${i} + 1 ) }'
********************************************