Menu: Difference between revisions

=={{header|Prolog}}==

<lang prolog>

rosetta_menu([], "") :- !. %% Incase of an empty list.

rosetta_menu(Items, SelectedItem) :-

repeat, %% Repeat until everything that follows is true.

display_menu(Items), %% IO

get_choice(Choice), %% IO

number(Choice), %% True if Choice is a number.

nth1(Choice, Items, SelectedItem), %% True if SelectedItem is the 1-based nth member of Items, (fails if Choice is out of range)

!.

display_menu(Items) :-

nl,

foreach( nth1(Index, Items, Item),

format('~w) ~s~n', [Index, Item]) ).

get_choice(Choice) :-

prompt1('Select a menu item by number:'),

read(Choice).

</lang>

Example run:

<lang prolog>

?- rosetta_menu(["fee fie", "huff and puff", "mirror mirror", "tick tock"], String).

1) fee fie

2) huff and puff

3) mirror mirror

4) tick tock

Select a menu item by number:a.

1) fee fie

2) huff and puff

3) mirror mirror

4) tick tock

Select a menu item by number:10.

1) fee fie

2) huff and puff

3) mirror mirror

4) tick tock

Select a menu item by number:3.

String = "mirror mirror".

</lang>