(no subject)

[Santiago]

I am playing with macros for getting some 2D arrays working, and i got something wrong when usin element 0 of array.
the code is this:
Great Cow BASIC (0.94 2015-08-05)

#chip mega328p, 16

create2Darray( my2Da, 8, 4 )     ' Create 2x4 Array called my2Da

set2Ddata( my2Da, 2, 4, 24 )     ' Set element 2,4 in array to 24

myvar = 0
get2Ddata( my2Da, 2, 4, myVar )  ' Get element 2,4 and put in myVar

do
loop

Macro create2Darray( name, size, dimY )
    Dim name( size )
    name(0) = dimY
End Macro

Macro set2Ddata( name, ordx, ordy, value )
    name( (ordx-1)*name(0)+ordy ) = value
End Macro

Macro get2Ddata( name, ordx, ordy, var )
    var = name( (ordx-1)*name(0)+ordy )
End Macro

I se that gcbasic creates an alias for element 0 and sets its value properly:
;Alias variables

;Alias variables
#define SYSMY2DA_0  256
...
...
    ldi SysValueCopy,4
    sts SYSMY2DA_0,SysValueCopy

And uses it in the macro set2Ddata, for example the line in file.gcb:

set2Ddata( my2Da, 2, 4, 24 )

generates this code in file.asm:

    ldi SysValueCopy,4
    sts SYSMY2DA_0,SysValueCopy
    ldi SysValueCopy,24
    sts SysArrayTemp1,SysValueCopy
    lds SysTemp2,SYSMY2DA_0    ;<<<<<<<<<<
    ...
    ...

In the macro get2Ddata i use exactly the same calculations.
but the line in file.gcb:

get2Ddata( my2Da, 2, 4, myVar )

gerenates this asm:

    lds SysTemp2,MY2DA0     ;<<<<<<
    ldi SysTemp3,low(MY2DA)
    add SysTemp2,SysTemp3
    ...
    ...

Then looking in the memory location of variables i see:

;Set aside memory locations for variables
.EQU    MY2DA=256
.EQU    MY2DA0=265  ;<<<<<<<<<<<<
.EQU    MYVAR=266
.EQU    SysArrayTemp1=267
.EQU    SysPointerX=268

MY2DA0 is not in my code and was generated by gcbasic and used in place of SYSMY2DA_0 only in the get macro.
Finally i got my code working properly this way:

Macro set2Ddata( name, ordx, ordy, value )
    index = (ordx-1)*name(0)+ordy
    name( index ) = value
End Macro

Macro get2Ddata( name, ordx, ordy, var )
    index = (ordx-1)*name(0)+ordy
    var = name( index )
End Macro

This way the variable MY2DA0 is not created and the alias SYSMY2DA_0 is properly used in both macros.
I know my code is a bit tricky but may be there is something in the compiler.

[Chris Roper]

In GCBasic arrays are indexed from 1, there is no element zero.
The First element, zero, of the array stores the length of the array.

Cheers
Chris