QB64/QB64-website
QB64/QB64-website
1
1
Fork 0
mirror of https://github.com/DualBrain/QB64.git synced 2023-11-19 13:10:13 +00:00
Code Issues Releases Wiki Activity
QB64-website/wiki/REDIM.md
Cory Smith ca88ba2965 More wiki experiment.
2022-12-24 19:12:43 -06:00

2.9 KiB
Raw Permalink Blame History

A REDIM statement can re-dimension one $DYNAMIC(flexible) Arrays or a comma separated list of arrays.

Syntax

REDIM [_PRESERVE] [SHARED] ArrayName[type_suffix] ({max_element | low_element[TO upper_element, ...]}) [AS Type]

REDIM [_PRESERVE] [SHARED] [AS Type] ArrayName({max_element | low_element[TO upper_element, ...]})

Description

  • Can change the number of elements in an array (the present array data is lost unless _PRESERVE is used).
  • Dynamic array elements can also be sized or resized by a program user's entry.
  • The _PRESERVE option also allows the element range values to be moved upward or downward.
  • Array is the name of the array to be dimensioned or re-dimensioned.
  • elements is the number of elements the array should hold. Use the optional TO elements2 to set a range.
  • Always use the same array TYPE suffix (AS type) or a new array type with the same name may be created.
  • REDIM cannot change $STATIC arrays created with a DIM statement unless the $DYNAMIC metacommand is used.
  • To create a dynamic array use the $DYNAMIC metacommand or use REDIM rather than DIM when first creating the array.
  • Use REDIM _PRESERVE to change the range or number of array elements without losing the remaining elements. Data may move up or down to accommodate those boundary changes.
  • REDIM _PRESERVE cannot change the number of array dimensions or type.
  • $DYNAMIC arrays MUST be REDIMensioned if ERASE or CLEAR are used to clear the arrays as they no longer exist.
  • When AS is used to declare the type, use AS to retain that type or it will change to SINGLE!
  • Warning! Do not use negative array upper bound index values as OS access or "Out of Memory" ERROR Codes will occur.
  • When using the AS type variable-list syntax, type symbols cannot be used.

Example(s)

The $DYNAMIC metacommand allows an array to be re-sized using DIM and REDIM.


'$DYNAMIC

INPUT "Enter array size: ", size 
DIM Array(size)

REDIM Array(2 * size)

PRINT UBOUND(Array)

Shows the difference between REDIM and REDIM _PRESERVE.


REDIM array(20)
array(10) = 24

PRINT array(10)

REDIM _PRESERVE array(30)
PRINT array(10)

REDIM array(15)
PRINT array(10) 



 24
 24
 0

Explanation: REDIM without _PRESERVE erases the array data and cannot change the number of dimensions.

See Also