Rf_asChar: Coerce an R object to a scalar string (CHARSXP)

In ramiromagno/c3po: From C to R and back again

Description

\Sexpr[results=rd, stage=render]{c3po:::badge('fnp')} \Sexpr[results=rd, stage=render]{c3po:::badge('r2r')} \Sexpr[results=rd, stage=render]{c3po:::badge('prot')}

Coerce an R object to a scalar string, i.e., to an R object of type CHARSXP. This object type should only be used internally, i.e., it should not be returned back to R.

Arguments

x	a pointer SEXP.

Value

A pointer SEXP, referring to an object of type CHARSXP.

Declaration

SEXP asChar(SEXP x);

In Rinternals.h.

Definition

SEXP asChar(SEXP x)
{
  if (isVectorAtomic(x) && XLENGTH(x) >= 1) {
    int w, d, e, wi, di, ei;
    char buf[MAXELTSIZE];  /* Probably 100 would suffice */

      switch (TYPEOF(x)) {
        case LGLSXP:
          if (LOGICAL(x)[0] == NA_LOGICAL)
            return NA_STRING;
        if (LOGICAL(x)[0])
          sprintf(buf, "TRUE");
        else
          sprintf(buf, "FALSE");
        return mkChar(buf);
        case INTSXP:
          if (INTEGER(x)[0] == NA_INTEGER)
            return NA_STRING;
        snprintf(buf, MAXELTSIZE, "%d", INTEGER(x)[0]);
        return mkChar(buf);
        case REALSXP:
          PrintDefaults();
        formatReal(REAL(x), 1, &w, &d, &e, 0);
        return mkChar(EncodeReal0(REAL(x)[0], w, d, e, OutDec));
        case CPLXSXP:
          PrintDefaults();
        formatComplex(COMPLEX(x), 1, &w, &d, &e, &wi, &di, &ei, 0);
        return mkChar(EncodeComplex(COMPLEX(x)[0], w, d, e, wi, di, ei, OutDec));
        case STRSXP:
          return STRING_ELT(x, 0);
        default:
          return NA_STRING;
      }
  } else if(TYPEOF(x) == CHARSXP) {
    return x;
  } else if(TYPEOF(x) == SYMSXP)
    return PRINTNAME(x);
  return NA_STRING;
}

In util.c.

See Also

R_CHAR

Examples

# Coerces an R object to an object of type CHARSXP
print_char <- inline::cfunction(c(x = "any"),
' const char * x_;
  x_ = R_CHAR(Rf_asChar(x));
  Rprintf("%s\\n", x_);
  return R_NilValue;
')

# Convert from STRSXP to CHARSXP
invisible(print_char("coal"))
invisible(print_char(c("charcoal", "coal")))
invisible(print_char(NA_character_))

# Convert from LGLSXP to CHARSXP
invisible(print_char(TRUE))
invisible(print_char(FALSE))
invisible(print_char(NA))

# Convert from INTSXP to CHARSXP
invisible(print_char(-1L))
invisible(print_char(1L))
invisible(print_char(NA_integer_))

# Convert from REALSXP to CHARSXP
invisible(print_char(1.0))
invisible(print_char(-1))
invisible(print_char(NA_real_))

# Convert from CPLXSXP to CHARSXP
invisible(print_char(2+5i))

# Convert from SYMSXP to CHARSXP
invisible(print_char(as.symbol('a')))

# Coercion from other object types to CHARSXP
# results in NA:
# From VECSXP to CHARSXP
invisible(print_char(list(a = 'b')))
# From ENVSXP to CHARSXP
invisible(print_char(.GlobalEnv))
# From CLOSXP to CHARSXP
invisible(print_char(function() {}))
# From EXPRSXP to CHARSXP
invisible(print_char(expression()))
# From LANGSXP to CHARSXP
invisible(print_char(~ 2 + x))

ramiromagno/c3po documentation built on Jan. 5, 2021, 8:01 p.m.