60 lines
1.9 KiB
Markdown
60 lines
1.9 KiB
Markdown
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Real
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---
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Real is a c-based interface for connecting R to Prolog.
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YAP introduces a development version of real, developed to experiment
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with the internals of the implementation of R. It includes major
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changes and is likely to be much less stable than the version
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maintained by Nicos ANgelopoulos. We refer to the version herein as
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'realC' and describe the main novelties vs the version described
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in~\cite{}. Their major differences:
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- Most of realC is written in `C`, instead of aa a Prolog string
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generator. The `C` code respects the SWI-Prolog fli interface and
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should work both in YAP and in SWI-Prolog.
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- realC uses Prolog atoms to represent real variables. R sequences
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of characters are represented as Prolog strings (not as lists of
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character codes). The atoms `true` and `false` indicate boolean
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constants.
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By default, YAP represents sequences of codes using double
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quotes, and strings by back quotes. Please consult the
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documentation o the ISO-Prolog flag `double_quotes` if you using
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prefer reading double-quote strings as Prolog string.
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- Free variables can be used to represent missing
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arguments,ie. `a[_,"G23"] would represent the column "G23".
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- All recent versions of real support the common syntax extensions
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for [], (), thus realC allows writing `a[[2]] <- f().
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- YAP allows A.B to be interpreted as [A|B]. This version takes
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advantage of this implementation quirk, and allows one to write
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expressions such as `a.b[2] <- f.g()`.
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- The left-hand side msy be:
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+ a ground unary term, assumed to be an attribute
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+ an index
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+ an R variable
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+ a logic variable, or other Prolog term: in this case it will be
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unified with the result of evaluating the right-hamd side.
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Yap
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?- [examples/for_real].
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?- for_real.
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---
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Nicos Angelopoulos and Vitor Santos Costa
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December, 2012.
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Updates: Nicos Angelopoulos
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Dec. 2013,
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March, 2014
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Updates: Vitor Santos Costa
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Dec. 2015
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