As discussed in section 2.18, SWI-Prolog supports international character handling. Its internal encoding is UNICODE. I/O streams convert to/from this internal format. This section discusses the options for source files not in US-ASCII.
SWI-Prolog can read files in any of the encodings described in
section 2.18. Two encodings are
of particular interest. The
text encoding deals with the current locale, the
default used by this computer for representing text files. The encodings
UNICODE encodings: they can represent---in the same
file---characters of virtually any known language. In addition, they do
If one wants to represent non US-ASCII text as Prolog terms in a source file, there are several options:
\. The numerical argument is interpreted as a UNICODE character.29To my knowledge, the ISO escape sequence is limited to 3 octal digits, which means most characters cannot be represented. The resulting Prolog file is strict 7-bit US-ASCII, but if there are many NON-ASCII characters it becomes very unreadable.
:- encoding(utf8).Many of today's text editors, including PceEmacs, are capable of editing UTF-8 files. Projects that were started using local conventions can be re-coded using the Unix iconv tool or often using commands offered by the editor.