The precise place for this is the standard, ISO/IEC 13211-1:1995, quoted_token (* 6.4.2 *)
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The precise syntax is quite complex due to a lot of extras like continuation lines and the like. If you are only writing atoms that should be read by Prolog, things are a bit easier. Also in that situation, you could always quote, which makes writing again a bit simpler.
Some things to be aware of:
Only simple spaces may occur as layout in a quoted atom. All other spaces need to be escaped like \t
, \n
(abrftnv
). Many systems accept also other layout but they differ to each other in very tiny details.
Backslash and quote must be escaped.
Characters outside the printable ASCII range depend on the PCS supported by a system. In a conforming system, the accompanying documentation should define how the additional characters (extended characters) are classified. Documentation quality varies on a wide range.
In any case, test your interface also with GNU-Prolog from 1.4.1 upwards. To date, no differences are known between GNU 1.4.1+ and the standard as far as syntax is concerned.
Here are some 240+ syntax related test cases. Please report any oversight!