[R] A question in Rinternals.h

[PO SU]

Dear Rusers,
    when i am reading Rinternals.h file, i can't understand the following codes in lines 395-407:


#define CHAR(x)R_CHAR(x)
const char *(R_CHAR)(SEXP x);
/* Various tests with macro versions below */
Rboolean (Rf_isNull)(SEXP s);
Rboolean (Rf_isSymbol)(SEXP s);
Rboolean (Rf_isLogical)(SEXP s);
Rboolean (Rf_isReal)(SEXP s);
Rboolean (Rf_isComplex)(SEXP s);
Rboolean (Rf_isExpression)(SEXP s);
Rboolean (Rf_isEnvironment)(SEXP s);
Rboolean (Rf_isString)(SEXP s);
Rboolean (Rf_isObject)(SEXP s);


I can't figure out what are "R_CHAR,Rf_isNull....Rf_isObject" meaning, they seem like function declarations, Rf_XXX maybe function pointers?
I need your help.




--

PO SU
mail: desolator88 at 163.com
Majored in Statistics from SJTU
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