[Coco] A bug in Basic09/RunB

[Robert Gault]

Willard and All,

Let's but this "bug" to rest. I've just spent some time reading the 
manual for Basic09 and this example of parameter passing with (a+0) is 
not a bug!

Basic09 performs automatic type conversions on expressions containing 
mixed numerical data types. "The result is always of the same type as 
the value having the largest representation, in the order: real < 
integer < byte."
Basic09 passes parameters either by reference or value. Passing a 
variable by reference makes it possible for the receiving procedure to 
change the variable. Passing by value protects variables because the 
receiving procedure can't change them. (x+0) passes a numeric value 
while (x$+"") passes a string value.

Regards the "bug", you may be asking what type of data is 0? That is the 
crux of the matter. 0 is an integer not a byte! Based on the above you 
should expect the passed value (x+0) to be an integer regardless of how 
x is defined. However, there is no need to speculate.
"The results of expressions containing numeric constants are either 
integer or real values; there are no byte constants. To send byte-type 
variables to a procedure, pass the values by reference. Therefore, if a 
RUN statement evaluates an integer as a parameter and sends it to a 
byte-type variable, the byte variable uses only the high-order byte of 
the two-byte integer."
The result of x+0 is an integer because 0 is an integer making the 
passed data an integer.

These quotes are from the OS-9 Owner's Manual, chapter 6 covering Basic09.