ASC() returns a negative number from single char.

[DJLinux]

for i=1 to 5
  c$=ReadChar(f) 
  print asc(c$) +","
next

if ReadChar() reads a single byte betweeen 0-255
ASC(c$) should never return "-161" ?!?


You can see the sign bit is set 0x8C
but i would accept from ReadByte() function a number between -128 and +127
not from ASC(c$) function

or i'm wrong ?

as a workaround i use
c$=chr$(Readbyte(f) and 127)


Joshy

[Nicky Peter Hollyoake]

I'm not to sure the problem because I get no negative numbers, but you could always use ... "ABS ( ASC ( Char ))"?

- Nicky

[DJLinux]

no ABS() is wrong
abs(-161) = 161
c$ = 0x8C = 140 decimal
proof it self
8*16+12=140


a char is between 0 and 255
a byte is between -128 and +127
a unsigned byte 0 and 255

now if you have in a file a letter with code 140
c$=ReadChar(hFile)
ASC(c$) returns -161 not 140
and an ABS(-161) isn't 140

Joshy

[dw817]

Nope, Nicky.
It's a real error, and it's not just file related. Can repeat error here a different way:

dim c$=chr$(-116)
print asc(c$)

Should return positive # in all cases or cry an error of boo hoo for no negative # for chr$()
Does neither. I see ASCII does return a negative #. I'm - not sure who this would affect if changed, however, I would prefer it 0-255 instead of -128 to 127 as it is now.

Hope This Helps !

[dw817]

Bump.

Did anyone ever fix this error ?

Tried it again on B4GL v2.5.8.

cls
dim a$
a$=chr$(-1)
printr a$
printr asc(a$)
drawtext()
end

results:
Y
-1

I think we're gonna have to be very careful and not accidentally feed a negative number into ASC function or get really fouled up answers.