[m-users.] [Beginner] How to pretty print a list of lists of strings

[Julien Fischer]

On Fri, 14 Oct 2022, Razetime wrote:

> I have a list [["abc","bcd"],["acb","cbd"]] and I would like to
> prettyprint it to an IO stream.
>
> I looked into the pretty_print module but it seems to be for
> generating documentation,

It isn't for generating documentation. I guess the point of confusion
is that it refers to docs, but in the context of pretty_printer module
these are references to the doc/0 type defined by that module.
That type can be used to format arbitrary Mercury terms (and more
generally constuct documents potentially containing arbitrary Mercury
terms).

To pretty-print the above term to stdout using the pretty_printer
module, you could just do:

      L = [["abc","bcd"],["acb","cbd"]],
      pretty_printer.write_doc_formatted(L, !IO)

> and format from the io and strings module seems to be for simpler
> types. How would I go about doing this? I want to know if there's
> something i can use from the stdlib, similar to show in haskell.

I haven't used Haskell in quite some time, so I can remember the
exact semantics of show, however ...

In the string module, the function string/1 will convert an arbitrary
term into a string representation.

The io module has the print family of functions (io.print/3, io.print/4
io.print_line/3 etc.) and the write family of function (io.write/3,
io.write/4, io.write_line/3 etc.).  The distinction between the two
is that the print family are supposed to be human readable, whereas
the output of the write family are supposed to valid Mercury syntax.

Julien.