cast to char

[mike sander]

I have been working on tests for cast().  i have run into some 
inconsistent behaviour with casting to char type.    casting any numeric 
type to any other numeric type (and logical) seems well behaved.  In 
cases where the input value is outside the range of the output type, the 
output is set to the min/max of the output type as would be expected.

With cast to char, the behavior is different.  Here are a couple of 
simple examples using direct type conversion:


Case 1: expect char 0  (got undefined). equivalent to cast ( int8(-128), 
"char")
>> x=int8(-128)
x = -128
>> z=char(x)
warning: range error for conversion to character value
error: value on right hand side of assignment is undefined

Case 2: expect char 0 (got 0.  this one works as expected). Equivalent 
to cast(single(-128),"char")
>> x=single(-128)
x = -128
>> z=char(x)
warning: range error for conversion to character value
z =
>> single(z)  # use this to output a printable value
ans = 0
>>

Case 3: expect char 255  Equivalent to cast(single(1000),"char")
>> x=single(1000)
x =  1000
>> z=char(x)
warning: range error for conversion to character value
z =
>> single(z) # use this to output a printable value
ans = 0


My initial question is whether cast to char should work as it does for 
numeric types?    If not, is there information available on how this 
should work?    If so, I see a couple of changes that should be made:

1) ov-base-int.cc octave_base_int_scalar<T>::convert_to_str_internal() 
should compute retval in all cases to eliminate undefined in Case 1.
2) dont return 0 for all out of range inputs.  The various 
convert_to_str_internal() functions should handle ival < min char value 
& ival > max char value as separate cases & return 0/255 in the case of 
out of range inputs.
3) none of the numeric conversions report range errors.  are these 
necessary for char conversion?


With these changes, cast to char would behave similarly to numeric 
types.    Any guidance is appreciated.

Are any of the above bugs that i should file?

Mike S