[Info-vax] Significance of 2020 / 2021 date

[1tim....@gmail.com]

On Saturday, January 9, 2021 at 3:11:04 PM UTC-7, Stephen Hoffman wrote:
> On 2021-01-09 21:38:07 +0000, 1tim.... at gmail.com said: 
> 
> > On Thursday, January 7, 2021 at 2:00:26 PM UTC-7, issinoho wrote: 
> >> ... 
> >> if (atoi (date_string + 5) > 2020). 
> >
> > you are adding 5 to the ascii value of the first byte of that date string.
> The cited C code above is not adding 5 to the ASCII value of the first 
> byte. The date_string + 5 syntax shown is performing pointer math, and 
> moves the begining of the string by five of whatever the pointer is 
> pointing to. That'll be 5 characters, if date_string is a character 
> pointer as would be typical. 
> 
> A word or longword pointer would be somewhat unusual here, though 
> pointer math works with that, too. Adding 5 would relocate by 10 or by 
> 20 bytes for a word or longword pointer, respectively. But I digress. 
> 
> If this is a request to add 5 to the ASCII value of the first byte, 
> then the code would typically be date_string[0] + 5, or maybe 
> *date_string + 5, assuming a character pointer. date_string[0] and 
> *date_string both return the byte value for the specified pointer, 
> again assuming a character pointer. 
> 
> > code should read 
> > if ((atoi(date_string) + 5) > 2020)' 
> 
> That C code will convert the contents of the bytes at the specified 
> address to an integer, then add 5 to the result. 
> 
> (Valid input for atoi can include an optional leading + or -, then some 
> number of decimal digits up to the first non-decimal-digit or the first 
> null byte. Invalid string input gets a 0 as a return from atoi.) 
> 
> But without more context to the code, it's difficult to determine the 
> intent of the programmer with absolute certainty. 
> 
> Hoff
> -- 
> Pure Personal Opinion | HoffmanLabs LLC

this is me jumping between languages again. :-(