SWI-Prolog程序

Question

任务:将源文件中包含指定字符串的所有行作为片段写入新文件，该片段是从键盘输入的。

我不知道如何将Prolog中来自文件的行逐行与我从键盘输入的片段进行比较，并将匹配的行输出到新文件中。我将很高兴收到任何建议或指导。我不能在开场白中直接思考。

f:-    
   write('Enter the name of the source file:'),  
   read(SOURFILE), 
   check_exist(SOURFILE), 
   open(SOURFILE,read,FROM),
   read_line_to_string(FROM,X),writef(" "),
   writef(X),
   writeln(" "),
   write('Enter a substring:'),
   read(WR),
   close(FROM),
   write('Enter the name of the new file:'),
   read(NEWFILE),
   check_exist(NEWFILE),
   name(S,X),
   write_to_file(NEWFILE,S).
        
check_exist(Filename):-exists_file(Filename),!.
   check_exist(_):-writeln('There is no such file'),
   fail.

write_to_file(Filename,TEXT) :-
   open(Filename, write, File),
   write(File, TEXT),nl,
   writeln('Data recorded successfully'),
   close(File).

Answer 1

在SWI-Prolog中，您可以使用谓词sub_string/5来验证字符串是否包含子字符串。因此，要解决您的问题，您可以这样做：

copy(From, To, Substring) :-
   open(From, read, Input),
   open(To, write, Output),
   repeat,
   read_line_to_string(Input, String),
   (   String = end_of_file
   ->  !        % stop reading lines
   ;   sub_string(String, _, _, _, Substring),
       writeln(Output, String),
       fail ),  % backtracks to read next line
   close(Input),
   close(Output).