String Arrays -- indices

[Chris Chancellor]

Hello Charles

i had modified your ARRAY OF ARRAYS USING STRINGS program

and i can't figure out how your macro aa works?

Code Select Expand


'ACCESS ARRAY (USING INDEXBASE 1)
=================================
macro aa int* (va,ix,iy)
  @va=strptr sy(iy)+(ix)*4-4
end macro


especially the term  (ix)*4-4  
is this term an index to the array sy[ ]  ?

is macro aa meant for  2 dimensional array so that the term  (ix)*4-4  
is an index pointer to the second dimension of the array sy[]


Here is a modification of your code :

Code Select Expand


'11:10 31/05/2018
'ARRAY OF ARRAYS USING STRINGS

$ filename "String_Array.exe"
       uses rtl64


' http://www.oxygenbasic.org/forum/index.php?PHPSESSID=61ht1jfjq4f4854dmu41q84ov0&topic=1694.msg18411;topicseen#msg18411
'CREATE ARRAY FOR INTs
======================
string sy[100] 'STRING BUFFERS
int i
for i=1 to 100
  sy[i]=nuls 50*sizeof int 'dim int sx[50]
  sy[i] = i
next
'
'ACCESS ARRAY (USING INDEXBASE 1)
=================================
macro aa int* (va,ix,iy)
  @va=strptr sy(iy)+(ix)*4-4
end macro

'TESTS:
=======
aa(2,3)=42
aa(20,30)=100
print " aa(2,3)*aa(20,30)  : "  aa(2,3)*aa(20,30)


print  " aa(1,1)  : "       aa(1,1)
print  " aa(2,1)  : "       aa(2,1)
print  " aa(3,1)  : "       aa(3,1)





[Charles Pegge]

Hi Chris,

The intent of this code was to show that arrays-of-arrays are possible, though not desirable if all you need is a regular 2d array.

The data buffer is an array of strings, and each string holds a row of data.

The macro function is used to access the array, assuming the elements are integers using indexbase 1 indexes.

I've changed the expression slightly to clarify how the address of va is calculated: va is the return variable.

macro aa int* (va,ix,iy)
  @va=strptr(sy(iy)) +(ix)*4  -4
end macro



My code:

Code Select Expand


'ARRAY OF ARRAYS USING STRINGS

'CREATE ARRAY FOR INTs
======================
string sy[100] 'STRING BUFFERS
int i
for i=1 to 100
  sy[i]=nuls 50*sizeof int 'dim int sx[50]
next
'
'ACCESS ARRAY (USING INDEXBASE 1)
=================================
macro aa int* (va,ix,iy)
  @va=strptr(sy(iy)) +(ix)*4-4
end macro

'TESTS:
=======
aa(2,3)=42
aa(20,30)=100
print aa(2,3)*aa(20,30)


[Chris Chancellor]

Thanxx Charles

could you please provide an example of a 2 D string array?