> For the complete documentation index, see [llms.txt](https://richardweiyang-2.gitbook.io/systemtap_with_examples/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://richardweiyang-2.gitbook.io/systemtap_with_examples/language/function_macro.md).

# Function & Macro

The concept is simple, what we need to know is the format in systemtap.

## Function and Macro

This is a similar concept as in c with a little different in keywords. And a function could be defined with type declaration or not.

For more information, you could read [Ref 1](https://sourceware.org/systemtap/man/stap.1.html#lbAJ)

```
@define add(a,b) %( ((@a)+(@b)) %)

function series(a)
{
    sum = 0;
    idx = 0;
    while (idx < a)
        sum += idx++;
    return sum;
}

// function with type declaration
function sum:long (a:long, b)
{
    return a + b;
}

probe begin
{
    // invoke a function
    printf("%d\n", series(5));
    // invoke a function with type declaration
    printf("%d\n", sum(1, 2));
    // invoke a macro
    printf("%d\n", @add(1, 2));
    exit();
}
```