Compute property arithmetically - jenkins

Question

In short I am not able to make a computation based on a property within my build file.
Let's say I have:
<property name="basedir" value="${project.basedir}" /> <--Current value 73
How can I know the previous 3 builds (72,71 and 70) OR how can I compute these values(based on the basedir property)?
I have tried (ignore the addition):
<property name="basedir" value="${project.basedir}+1" /> <--But it concats the value: 73+1
<property name="basedir" value="${project.basedir+1}" /> <--But it is just wrong: build_${env.BUILD_NUMBER+1}
Scenario: Remove old releases (keep some releases in case of a rollback)
P.S: The duplicate link is invalid because this is a deployment via PHING not ANT

Answer 1

You could use an adhoc-task for this:
<?xml version="1.0"?>
<project default="main" phingVersion="2.11.0">
<property name="basedir" value = "73"/>
<adhoc-task name="increment"><![CDATA[
class increment extends Task {
private $value;
function setvalue($value) {
$this->value = $value;
}
function setProperty($property) {
$this->property = $property;
}
function main() {
$this->project->setProperty($this->property, ((int) $this->value + 1));
}
}
]]></adhoc-task>
<target name="main">
<echo>${basedir}</echo>
<increment value="${basedir}" property="basedir"/>
<echo>${basedir}</echo>
</target>
</project>