Blocks

Blocks are elements, that execute their children in the order they appear, and return the result of the last child as their own result.

Blocks do not have their own scope, meaning that variables set inside a block are accessible outside of it, and variables set outside of a block are accessible inside it.

Many elements in XMLang are blocks, such as <program>, <block>, <loop>, ;<if>'s children, <try>'s children and functions.

<block>

The <block> element is used to create a block of code that can be executed.

This is the simplest way to create a block, and it can be useful when you want to calculate a value inside another element's children, while returning a single value.

If no children are provided, the result of the block is null.

Example

<program>
    <print>
        The result of the block is:
        <space />
        <block>
            <set var="x"><int><readline /></int></set>
            <set var="x"><add><get var="x" /><int>1</int></add></set>
            <get var="x" /> <!-- Only the result of this child will be returned -->
        </block>
    </print>
</program>

<return>

The <return> element is used to return a value from a block or a function.

It stops the execution of the nearest block or function and returns a value to the caller.

No further elements after <return> are executed.

Children

It accepts at most a single child, which is evaluated and returned as the result of the block or function.

If no child is provided, the result of the block or function is null.

Example

<program>
    <print>
        The result of the block is:
        <space />
        <block>
            <set var="x"><int><readline /></int></set>
            <set var="x"><add><get var="x" /><int>1</int></add></set>
            <return><get var="x" /></return>
            <print>This will never be printed.</print>
        </block>
    </print>
</program>