在 SWI-Prolog 中写入格式化文本

发布于 2024-12-08 06:43:56 字数 638 浏览 0 评论 0原文

我在 SWI-Prolog 文档上花费了大量时间，但一无所获。我的愿望是能够格式化输出的数字，以便我控制显示的总小数位数，并在给定的字符宽度中右对齐数字。例如：

  2.500   (trailing zeroes displayed)
 34.432   (rounded from a much longer decimal value)
213.110

所有 3 个都在 7 个字符宽的空间中右对齐，显示 3 位小数（即使这些数字为零）。我可以单独完成其中一些事情，但不能一次全部完成。

writef( '%7R', [34.342]).
writef( '%7R', [34.300]).

^^^ 这非常接近我想要的，但不幸的是它确实显示任何尾随零（它总是会忽略它们）。另外，在将舍入值传递给 writef() 之前，我必须手动进行舍入。

format( '~3f', 34.34219089).
format( '~3f', 1234.3).

这个进行舍入，并允许尾随零，但我找不到使用“格式”函数强制右对齐的方法，而且我找不到一种将 writef （对齐）功能与格式（舍入和零显示）。

有什么想法吗？

非常感谢！

原文

I have spent a significant amount of time in the SWI-Prolog documentation and am getting nowhere. My desire is to be able to format numbers that are output such that I am controlling total # decimal digits displayed and also right aligning the numbers in a given character width. For example:

  2.500   (trailing zeroes displayed)
 34.432   (rounded from a much longer decimal value)
213.110

All 3 are right aligned in a 7 character wide space, with 3 decimal places displayed (even when those are zero). I can accomplish some of these things individually, but not all at once.

writef( '%7R', [34.342]).
writef( '%7R', [34.300]).

^^^ This comes very close to what I want, but unfortunately it does display any trailing zeroes (it will always omit them). Also, I have to do the rounding manually before passing the rounded value to writef().

format( '~3f', 34.34219089).
format( '~3f', 1234.3).

This one does the rounding, and allows trailing zeroes, but I can find no way to force right alignment using the "format" function, and I can't find a way to combine the functionality of writef (alignment) with format (rounding and zero display).

Any ideas?

Thanks much!

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一个人练习一个人 2024-12-15 06:43:56

我遇到了同样的问题，甚至更多：

[debug]  ?- format( '~3f', 34.34219089).
34,342

逗号（尽管语言环境需要，但请注意这一点）使读回输出变得复杂。我最终得到了一些丑陋的解决方法来控制舍入：

[debug]  ?- X is round(34.34219089 * 1000) / 1000, write(X).
34.342
X = 34.342.

要填充和对齐，您应该使用制表位，由成对的 t 和 | 控制。文档在这个主题上有点过于综合。例如，要以电子表格默认样式（文本左对齐，数字右对齐）打印数字表：

test(indent) :- nl,
    forall(member(L, [[a,    3.66,      55.5334],
              [basd, 22.876345, 2113.4465],
              [cas,  0.6623233, 53.5]
             ]),
           format('~s~t~20|~t~3f~40|~t~3f~60|~n', L)).

请注意“空间分配器”说明符 ~t 的位置、绝对“列宽度”~|，考虑字段类型说明符。输出：

?- run_tests(sheet_inventory:indent).
% PL-Unit: sheet_inventory:indent 
a                                  3,660              55,533
basd                              22,876            2113,447
cas                                0,662              53,500

I got the very same problem, and more:

[debug]  ?- format( '~3f', 34.34219089).
34,342

The comma (albeit required by locale, watch out for this) complicates reading back the output. I ended up with some ugly workaround to control rounding:

[debug]  ?- X is round(34.34219089 * 1000) / 1000, write(X).
34.342
X = 34.342.

To pad and align you should use tab stops, controlled by pairs of t and |. Documentation it's a bit too much synthetic on this topic. For instance, to print a table of numbers in spreadsheet default style (text left align, number right align):

test(indent) :- nl,
    forall(member(L, [[a,    3.66,      55.5334],
              [basd, 22.876345, 2113.4465],
              [cas,  0.6623233, 53.5]
             ]),
           format('~s~t~20|~t~3f~40|~t~3f~60|~n', L)).

Note the position of 'space allocator' specifier ~t, the absolute 'column width' ~|, regards the field type specifier. The output:

?- run_tests(sheet_inventory:indent).
% PL-Unit: sheet_inventory:indent 
a                                  3,660              55,533
basd                              22,876            2113,447
cas                                0,662              53,500

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