[Rd] Spurious warnings in coercion from double/complex/character to raw

[Hervé Pagès]

Hi,

The first warning below is unexpected and confusing:

   > as.raw(c(3e9, 5.1))
   [1] 00 05
   Warning messages:
   1: NAs introduced by coercion to integer range
   2: out-of-range values treated as 0 in coercion to raw

The reason we get it is that coercion from numeric to raw is currently 
implemented on top of coercion from numeric to int (file 
src/main/coerce.c, lines 700-710):

     case REALSXP:
         for (i = 0; i < n; i++) {
//          if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt();
             tmp = IntegerFromReal(REAL_ELT(v, i), &warn);
             if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) {
                 tmp = 0;
                 warn |= WARN_RAW;
             }
             pa[i] = (Rbyte) tmp;
         }
         break;

The first warning comes from the call to IntegerFromReal().

The following code avoids the spurious warning and is also simpler and 
slightly faster:

     case REALSXP:
         for (i = 0; i < n; i++) {
//          if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt();
             double vi = REAL_ELT(v, i);
             if(ISNAN(vi) || (tmp = (int) vi) < 0 || tmp > 255) {
                 tmp = 0;
                 warn |= WARN_RAW;
             }
             pa[i] = (Rbyte) tmp;
         }
         break;

Coercion from complex to raw has the same problem:

   > as.raw(c(3e9+0i, 5.1))
   [1] 00 05
   Warning messages:
   1: NAs introduced by coercion to integer range
   2: out-of-range values treated as 0 in coercion to raw

Current implementation (file src/main/coerce.c, lines 711-721):

     case CPLXSXP:
         for (i = 0; i < n; i++) {
//          if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt();
             tmp = IntegerFromComplex(COMPLEX_ELT(v, i), &warn);
             if(tmp == NA_INTEGER || tmp < 0 || tmp > 255) {
                 tmp = 0;
                 warn |= WARN_RAW;
             }
             pa[i] = (Rbyte) tmp;
         }
         break;

This implementation has the following additional problem when the 
supplied complex has a nonzero imaginary part:

   > as.raw(300+4i)
   [1] 00
   Warning messages:
   1: imaginary parts discarded in coercion
   2: out-of-range values treated as 0 in coercion to raw

   > as.raw(3e9+4i)
   [1] 00
   Warning messages:
   1: NAs introduced by coercion to integer range
   2: out-of-range values treated as 0 in coercion to raw

In one case we get a warning about the discarding of the imaginary part 
but not the other case, which is unexpected. We should see the exact 
same warning (or warnings) in both cases.

With the following fix we only get the warning about the discarding of 
the imaginary part if we are not in a "out-of-range values treated as 0 
in coercion to raw" situation:

     case CPLXSXP:
         for (i = 0; i < n; i++) {
//          if ((i+1) % NINTERRUPT == 0) R_CheckUserInterrupt();
             Rcomplex vi = COMPLEX_ELT(v, i);
             if(ISNAN(vi.r) || ISNAN(vi.i) || (tmp = (int) vi.r) < 0 || 
tmp > 255) {
                 tmp = 0;
                 warn |= WARN_RAW;
             } else {
                 if(vi.i != 0.0)
                     warn |= WARN_IMAG;
             }
             pa[i] = (Rbyte) tmp;
         }
         break;

Finally, coercion from character to raw has the same problem and its 
code can be fixed in a similar manner:

   > as.raw(c("3e9", 5.1))
   [1] 00 05
   Warning messages:
   1: NAs introduced by coercion to integer range
   2: out-of-range values treated as 0 in coercion to raw

Cheers,
H.


-- 
Hervé Pagès

Bioconductor Core Team
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