Question

我正在使用以下谓词将数字转换为单词：

word(0) :- write('zero').
word(1) :- write('one').
word(2) :- write('two').
word(3) :- write('three').
word(4) :- write('four').
word(5) :- write('five').
word(6) :- write('six').
word(7) :- write('seven').
word(8) :- write('eight').
word(9) :- write('nine').
dash(X) :- 
    write('-'). %need to add some code here to not print dash after last dig
    

num_words(Nums) :- 
    Nums > 0,
    NMod is Nums mod 10,
    NDiv is Nums // 10,    	
    word(NMod),
    dash(Nums), 
    num_words(NDiv).

期望输出：

num_words(123) => one-two-three

当前输出：

num_words(123) => three-two-one-

查看我的输出，看起来我的逻辑几乎是正确的，但我没有意识到如何更改递归以“向后”打印数字，以便它们处于正确的顺序以及如何更改我的{{ 1}}谓词不能在最后一位数后打印短划线。

你们对如何解决这个问题有任何建议吗？

Answer 1

解决第一个或最后一个操作必须与其他操作不同的问题的技巧是将谓词拆分为两个。在这种情况下，您可以创建调用word(digit)的顶级谓词，然后调用另一个打印数字“尾部”的谓词，并在数字后面添加短划线。

此外，您需要重新安排递归，以便稍后计算稍后计算的数字。

num_words(Nums) :-       % This is top-level predicate.
    NDiv is Nums // 10,  % It prints the first digit unconditionally,
    dash_num_words(NDiv),% letting you handle the case when the number is zero.
    NMod is Nums mod 10, 
    word(NMod).

dash_num_words(0).       % When we reach zero, we stop printing.

dash_num_words(Nums) :-  % Otherwise, we follow your algorithm
    Nums > 0,            % with one modification: the dash is printed
    NDiv is Nums // 10,  % unconditionally before printing the digit.
    dash_num_words(NDiv),
    NMod is Nums mod 10,
    word(NMod),
    write('-').

Demo.

Answer 2

使用这篇文章：Split a number into a list of digits in Prolog您只需要使用递归谓词来打印结果列表。

word('0') :- write('zero').
word('1') :- write('one').
word('2') :- write('two').
word('3') :- write('three').
word('4') :- write('four').
word('5') :- write('five').
word('6') :- write('six').
word('7') :- write('seven').
word('8') :- write('eight').
word('9') :- write('nine').

num_words(X):- number_chars(X,C), printout(C).

printout([N]):- word(N),!.
printout([N|Tail]):- word(N),write('-'),printout(Tail).

请教：

?- num_words(1234567890).
 one-two-three-four-five-six-seven-eight-nine-zero
true.

我还更改了用引号括起数字的事实词。如果你不喜欢，我们可以改变它。

Answer 3

有关数字文字的更一般观点，请参阅this other answer。来自消息来源：

% Grammar for numbers, e.g.
% phrase(number(I),[two,hundred,and,fifty,six]).
% An astonishing characteristic of this code is that it's
% fully bidirectional. The expression
% phrase(number(256),Words)
% will instantiate Words = [two,hundred,and,fifty,six].
% What's more,
% phrase(number(I),Words)
% will eventually instantiate I and Words to all the numbers it knows.
%
% Ken Johnson 17-9-87

Prolog数字到单词

3 个答案: