allow a file filter with initialization.

docs/yap.tex

@@ -9113,14 +9113,24 @@ For every line @var{LineIn} in stream @var{StreamInp}, execute
 stream @var{StreamOut}.
 
 @item file_filter(+@var{FileIn}, +@var{FileOut}, +@var{Goal})
-@findex filter/3
+@findex file_filter/3
-@snindex filter/3
+@snindex file_filter/3
-@cnindex filter/3
+@cnindex file_filter/3
 
 For every line @var{LineIn} in file @var{FileIn}, execute
 @code{call(Goal,LineIn,LineOut)}, and output @var{LineOut} to file
 @var{FileOut}.
 
+@item file_filter(+@var{FileIn}, +@var{FileOut}, +@var{Goal},
++@var{FormatCommand},   +@var{Arguments})
+@findex file_filter_with_init/5
+@snindex file_filter_with_init/5
+@cnindex file_filter_with_init/5
+
+Same as @code{file_filter/3}, but before starting the filter execute
+@code{format/3} on the output stream, using @var{FormatCommand} and
+@var{Arguments}.
+
 @end table
 
 

library/lineutils.yap

@@ -11,10 +11,11 @@
 	   copy_line/2,
 	   filter/3,
 	   file_filter/3,
+	   file_filter_with_init/5,
 	   process/2
 	  ]).
 
-:- meta_predicate filter(+,+,:), file_filter(+,+,:), process(+,:).
+:- meta_predicate filter(+,+,:), file_filter(+,+,:), file_filter_with_init(+,+,:,+,:), process(+,:).
 
 :- use_module(library(lists),
 	      [member/2,
@@ -137,4 +138,12 @@ file_filter(Inp, Out, Command) :-
 	close(StreamInp),
 	close(StreamOut).
 
+file_filter_with_init(Inp, Out, Command, FormatString, Parameters) :-
+	open(Inp, read, StreamInp),
+	open(Out, write, StreamOut),
+	format(StreamOut, FormatString, Parameters),
+	filter(StreamInp, StreamOut, Command),
+	close(StreamInp),
+	close(StreamOut).
+