Subroutines and scripts

XSharper has a concept of a subroutine, that accepts 0 or more arguments and returns a single object value.

<!-- SUB1.XSH. Calculate squares of 20 and 50 -->

<xsharper>

        <set a="${=20}" />

        <call subId="square" outTo="result">

                <param>${a}</param>

        </call>

        <print>${a}*${a} = ${result}</print>

        <print>50*50 = ${=square(50)}</print>

        <!-- Subroutines -->

        <sub id="square">

                <param name="n" required="true" />

                <set ret="${=$n*$n}" />

                <return>${ret}</return>

        </sub>

</xsharper>

As seen above, subroutines may be invoked directly from the expressions.

To execute square subroutine from another script, it's possible to use include action:

<!-- SUB2.XSH. Calculate square of a value specified as a command-line argument -->

<xsharper>

        <include from="sub1.xsh" />

        <param name="v" required="true">Value to calculate square</param>

        <print>${v}*${v} = ${=square($v)}</print>

</xsharper>

Finally, execute another script as if it was executed from command line:

<!-- SUB3.XSH. Print square of a value using SUB2.XSH -->

<xsharper>

        <exec from="sub2.xsh">

                <param>500</param>

        </exec>

</xsharper>

Isolation level

By default, subroutines have read-only access to the variables of the caller and any set or changed variables in the subroutine body are restored.

<set x="50" />

<print>Before call x=${x}</print>

<call subId="sub" isolation="default" />

<print>After call x=${x}</print>

<sub id="sub">

        <print>Sub. Initially x=${x|'Undefined'}.</print>

        <set x="100" />         

        <print>Sub. Later x=${x}.</print>

</sub>

The code above will print:

Before call x=50

Sub. Initially x=50.

Sub. Later x=100.

After call x=50

This behaviour can be changed by caller, by changing attribute isolation

With isolation="none", when no variables are restored, the output will be

Before call x=50

Sub. Initially x=50.

Sub. Later x=100.

After call x=100

With isolation="high", the subroutine will have a totally clean variable list, w/o access to the caller variables at all:

Before call x=50

Sub. Initially x=Undefined.

Sub. Later x=100.

After call x=50