The `mapcar` Function

`mapcar` is a function that calls its first argument with each element of its second argument, in turn. The second argument must be a sequence.

For example,

```(mapcar '1+ '(2 4 6))
=> (3 5 7)
```

The function `1+` which adds one to its argument, is executed on each element of the list, and a new list is returned.

Contrast this with `apply`, which applies its first argument to all the remaining. (See section Readying a Graph, for a explanation of `apply`.)

In the definition of `one-fiftieth`, the first argument is the anonymous function:

```(lambda (arg) (/ arg 50))
```

and the second argument is `full-range`, which will be bound to `list-for-graph`.

The whole expression looks like this:

```(mapcar '(lambda (arg) (/ arg 50)) full-range))
```

See section `Mapping Functions' in The GNU Emacs Lisp Reference Manual, for more about `mapcar`.

Using the `one-fiftieth` function, we can generate a list in which each element is one-fiftieth the size of the corresponding element in `list-for-graph`.

```(setq fiftieth-list-for-graph
(one-fiftieth list-for-graph))
```

The resulting list looks like this:

```(10 20 19 15 11 9 6 5 4 3 3 2 2
1 1 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0 4)
```

This we are almost ready to print! (We also notice the loss of information: many of the higher ranges are 0, meaning that fewer than 50 defuns had that many words or symbols--but not necessarily meaning that none had that many words or symbols.)