Sorry if I’m missing something obvious but write mode doesn’t seem to be working for me here: I have a very small txt file which I’m reading with file_lines([]) --> []. file_lines([L|Ls]) --> [L], file_lines(Ls). test(File,Content) :- phrase_from_file(file_lines(Content), File). I’m…

[image] jan: Effefct of “write” option at the top-level - #2 by jan + works, thanks @jan . Do you want me to delete this post?

@jan can I ask one more quick question? I keep getting args not instantiated for this and can’t tell what I’m doing wrong file_lines([]) --> []. file_lines([L|Ls]) --> { string_codes(Char,[L]) }, [Char], file_lines(Ls). test(File,Content) :- phrase_from_file(file_lines(Content), …

You should swap two lines: file_lines([L|Ls]) → [Char], { string_codes(Char,[L]) }, file_lines(Ls).

Like this? file_lines([]) --> []. file_lines([L|Ls]) --> [Char], { string_codes(Char,[L]) }, file_lines(Ls). test(File,Content) :- phrase_from_file(file_lines(Content), File). I’m getting false 131 ?- trace, test('file.txt',Content). Call: (13) test('file.txt', _7680) ? cree…

I think that should be file_lines([]) --> []. file_lines([Char|Ls]) --> [Code], { string_codes(Char, [Code]) }, file_lines(Ls). because in a DCG [Code] will unify Code with a single code and so you want to turn that into a string (i.e. in CapeliC’s code, Char and L should be swapped)…

Thanks, yep that works, but it’s definitely counter intuitive. file_lines([]) --> []. file_lines([L|Ls]) --> [L], file_lines(Ls). L seems to unify with a code 109 ?- test('file.txt',Content). Content = [102, 111, 111, 10, 98, 97, 114, 10, 104|…] . So I thought my goal is to take the head…

Ah, sorry, I may have confused things by changing variable names. Your original code: file_lines([]) --> []. file_lines([L|Ls]) --> [L], file_lines(Ls). But we want L to be a single-character string instead: file_lines([]) --> []. file_lines([L|Ls]) --> [Char], % changed from L to Ch…

Even if we get this right though, the file is translated into a list of strings, each holding one character. I doubt that is the intend of the OP. What is the intend though? The name suggests a list of strings, one for each line?

Sorry @jamesnvc not completely sure I’m following. With file_lines([]) --> []. file_lines([L|Ls]) --> [L], file_lines(Ls). I’m seeing 105 ?- test('file.txt',Content), Content = [L|_]. Content = [102, 111, 111, 10, 98, 97, 114, 10, 104|…], L = 102 . Again, what I was attempting to do…

`w` write mode not working?

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jan April 13, 2026, 6:53am 2

See Effefct of "write" option at the top-level - #2 by jan

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`w` write mode not working?

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