31 lines
656 B
Markdown
31 lines
656 B
Markdown
|
## Chapter 4: Lists
|
||
|
|
|
||
|
|
Lists are enclosed in square brackets, and are finite sequences of elements.
|
||
|
|
Elements can be anything: `[mia, robber(yolanda), X, 2, mia]` or `[mia,
|
||
|
|
[vincent, jules], [butch, girlfriend(butch)]]` --- a list can contain other
|
||
|
|
lists.
|
||
|
|
|
||
|
|
Prolog lists use the standard head/tail vocabulary, and the decomposition operator is `|`:
|
||
|
|
|
||
|
|
```
|
||
|
|
[Head|Tail] = [mia, [vincent, jules], [butch, girlfriend(butch)]]
|
||
|
|
```
|
||
|
|
|
||
|
|
Note that the empty list behaves as one would think.
|
||
|
|
|
||
|
|
```
|
||
|
|
?- [X|Y] = [].
|
||
|
|
|
||
|
|
no
|
||
|
|
````
|
||
|
|
|
||
|
|
Arguments can be chained, such as `[X, Y | Z]`.
|
||
|
|
|
||
|
|
### The `member` function
|
||
|
|
|
||
|
|
```
|
||
|
|
member(X, [X|_]).
|
||
|
|
member(X, [_|T]) :- member(X, T).
|
||
|
|
```
|
||
|
|
|