<p>I have two functions, <code>f</code> and <code>g</code>, which call each other recursively. Unfortunately, when <code>f</code> calls <code>g</code>, it has not yet been declared, so I get an "unbound variable" error.  How can I prototype (or whatever the equivalent vocabulary is) this function in SML/NJ?</p>

Mutual Recursion. Use
```
and
```
instead of
```
fun
```
between the two functions.