[R] type checking --- just a thought

[A.J. Rossini]

S4 methods take care of some of this checking (more specification
needed). 

best,
-tony

ivo welch <ivo.welch at yale.edu> writes:

> hi:  would it be useful to build into R an optional mechanism that
> typechecks arguments?  for example,
>
>     sum.across <- function (  inpmatrix : matrixtype( dim[1]>1,
>     dim[2]>3 ) ) : vector { }
>        # this would define a sum.across function that can take
>        # matrices or data sets, but not vectors,
>        # and which indicates that it will return a vector.
>
>     xsum <- sum.across( 1:10 );  # error
>
>     repeat <- function( series : vector( dim>0 ),  times : scalar(
>     value>0 ) ) : vector;
>
> similarly, a common input error condition may be calling a function
> with a NULL vector, or with a vector with fewer than N observations.
> many statistical functions have such hard-wired limits.  I know that
> "if" statements can do this, but this might make for a nice
> standardized language feature.  on the other hand, the effort and
> complexity may not be worth the extra functionality.
>
> and one beg to the language maintainers for something that I hope is simple:
>
>     in R 1.8.2, please add to the "source" function information where
>     (file:linenumber) dies or ends.
>
> regards,
>
> /ivo
>
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Biomedical and Health Informatics   University of Washington
Biostatistics, SCHARP/HVTN          Fred Hutchinson Cancer Research Center
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