yap-6.3/packages/real

Real

Real is a c-based interface for connecting R to Prolog.

YAP introduces a development version of real, developed to experiment with the internals of the implementation of R. It includes major changes and is likely to be much less stable than the version maintained by Nicos ANgelopoulos. We refer to the version herein as 'realC' and describe the main novelties vs the version described in~\cite{}. Their major differences:

• Most of realC is written in C, instead of aa a Prolog string generator. The C code respects the SWI-Prolog fli interface and should work both in YAP and in SWI-Prolog.

• realC uses Prolog atoms to represent real variables. R sequences of characters are represented as Prolog strings (not as lists of character codes). The atoms true and false indicate boolean constants.

  By default, YAP represents sequences of codes using double quotes, and strings by back quotes. Please consult the documentation o the ISO-Prolog flag double_quotes if you using prefer reading double-quote strings as Prolog string.

• Free variables can be used to represent missing arguments,ie. `a[_,"G23"] would represent the column "G23".

• All recent versions of real support the common syntax extensions for [], (), thus realC allows writing `a2 <- f().

• YAP allows A.B to be interpreted as [A|B]. This version takes advantage of this implementation quirk, and allows one to write expressions such as a.b[2] <- f.g().

• The left-hand side msy be:

  • a ground unary term, assumed to be an attribute
  • an index
  • an R variable
  • a logic variable, or other Prolog term: in this case it will be unified with the result of evaluating the right-hamd side. Yap ?- [examples/for_real]. ?- for_real.

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Nicos Angelopoulos and Vitor Santos Costa December, 2012.

Updates: Nicos Angelopoulos Dec. 2013, March, 2014

Updates: Vitor Santos Costa Dec. 2015