[Coco] new problem with unpack

[Wayne Campbell]

It appears that one of the features of Basic09 is not a feature after all.
According to the Basic09 Reference for OS-9 Level 2:

Chapter 11: Basic09 Command Reference: LET
================================================================================
Use BASIC09’s assignment function to copy entire arrays or complex data
structures to another array or complex data structure. The data structures
do not need to be of the same type or shape, but the size of the
destination structure must be the same as or larger than the source
structure. This means the assignment function can perform unusual type
conversions. For example, you can copy a string variable of 80 characters
into a one-dimensional array of 80 bytes.
================================================================================

In the Level 1 Basic09 Manual it says:

Chapter 9: Program Statements and Structure: Assignment Statements: LET
================================================================================
Another use of the assignment statement is to copy the entire value of an
array or complex data structure to another array or complex data structure.
The data structures do not have to have the same type or "shape". The only
restriction is that the size of the destination structure be the same or
larger than the source structure. In fact this type of assignment can be
used to perform unusual type conversions. For example, a string variable of
80 characters can be copied to a one-dimensional array of 80 bytes.
================================================================================

Neither manual provides an example of this usage. I tried assigning a
string to an array and vice-versa. I even went back to OS-9 Level 2
original disk image and tried it with Basic09 01.00.01. The assignment does
not work in OS-9 or in NitrOS-9. It returns a ERROR #071. In ErrorCodes,
the message is:

Error#: 71 Illegal Expression Type

Here is a sample program to try. If you have a real CoCo2 or CoCo3, and you
run NitrOS-9 L1 or L2, please try this program. I need to know what happens
on the real hardware.

PROCEDURE LETtest
(* Remember that the keyword LET is optional *)
(* This procedure will use assignments both with and without it *)
(* I tried inserting BASE 1 and changing arrayStr length to 11 *)
(* with no change in the result *)

DIM array(10):BYTE
DIM arrayStr:STRING[10]
DIM posCount:INTEGER

(* array will contain 0123456789 *)
FOR posCount:=1 TO 10
  array(posCount):=posCount-1
NEXT posCount

arrayStr:=array \! error 71
PRINT arrayStr

arrayStr:="9876543210"
LET array:=arrayStr \! error 71
FOR posCount:=1 TO 10
  PRINT array(posCount);
NEXT posCount
PRINT

END

Load errors:

00C4 ERROR #071 Illegal Expression Type
00E4 ERROR #071 Illegal Expression Type

Error lines:

00BD arrayStr:=array <- C4 is the <eol> token
00C5 PRINT arrayStr

00DC LET array:=arrayStr <- E4 is the <eol> token
00E5 FOR posCount:=1 TO 10

Runtime error:

ERROR #051 Line with Compiler Error

So, while I am supposed to be able to do these types of assignments,
Basic09 does not, in fact, allow it. At least, not in VCC or in MESS. Note
that neither assignment statement shows an error in the editor. The syntax
is considered valid by Basic09's editor.

I believe that this functionality may have existed in L1 Basic09
(v01.00.00), but I do not have a copy to test with. I do, however, have a
copy of v01.00.01. Using that one I found the same error occurs. It is as
though this feature never really existed, but it could be that whatever
changed between v01.00.00 and 01.00.01 took away this feature.

I welcome any input that can help dispel this confusion. Does anyone else
on this list have experience with this form of assignment in Basic09?

Wayne