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75 lines
2.7 KiB
Markdown
75 lines
2.7 KiB
Markdown
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A REDIM statement can re-dimension one [$DYNAMIC]($DYNAMIC)(flexible) [Arrays](Arrays) or a [comma](comma) separated list of arrays.
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## Syntax
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> [REDIM](REDIM) [_PRESERVE] [SHARED] ArrayName[*typesuffix*] ({*max_element*|low_element[TO *upper_element*, ...]}) [AS Type]
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> [REDIM](REDIM) [_PRESERVE] [SHARED] [AS Type] ArrayName({*max_element*|low_element[TO *upper_element*, ...]})
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## Description
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* Can change the number of elements in an array (the present array data is lost unless [_PRESERVE](_PRESERVE) is used).
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* Dynamic array elements can also be sized or resized by a program user's entry.
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* The [_PRESERVE](_PRESERVE) option also allows the *element* range values to be moved upward or downward.
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* Array is the name of the array to be dimensioned or re-dimensioned.
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* elements is the number of elements the array should hold. Use the optional [TO](TO) elements2 to set a range.
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* **Always use the same array [TYPE](TYPE) suffix ([AS](AS) type) or a new array type with the same name may be created.**
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* REDIM cannot change [$STATIC]($STATIC) arrays created with a [DIM](DIM) statement unless the [$DYNAMIC]($DYNAMIC) [metacommand](metacommand) is used.
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* To create a dynamic array use the [$DYNAMIC]($DYNAMIC) metacommand or use [REDIM](REDIM) rather than [DIM](DIM) when first creating the array.
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* Use REDIM [_PRESERVE](_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.
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* **REDIM [_PRESERVE](_PRESERVE) cannot change the number of array dimensions or type.**
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* [$DYNAMIC]($DYNAMIC) arrays MUST be [REDIM](REDIM)ensioned if [ERASE](ERASE) or [CLEAR](CLEAR) are used to clear the arrays as they no longer exist.
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* When [AS](AS) is used to declare the type, use [AS](AS) to retain that type or it will change to [SINGLE](SINGLE)!
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* **Warning! Do not use negative array upper bound index values as OS access or "Out of Memory" [ERROR Codes](ERROR-Codes) will occur.**
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* When using the **AS type variable-list** syntax, type symbols cannot be used.
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## Example(s)
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The [$DYNAMIC]($DYNAMIC) metacommand allows an array to be re-sized using [DIM](DIM) and REDIM.
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```vb
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'$DYNAMIC
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INPUT "Enter array size: ", size
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DIM Array(size)
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REDIM Array(2 * size)
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PRINT UBOUND(Array)
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```
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Shows the difference between REDIM and REDIM [_PRESERVE](_PRESERVE).
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```vb
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REDIM array(20)
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array(10) = 24
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PRINT array(10)
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REDIM _PRESERVE array(30)
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PRINT array(10)
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REDIM array(15)
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PRINT array(10)
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```
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```text
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24
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24
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0
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```
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> *Explanation:* REDIM without _PRESERVE erases the array data and cannot change the number of dimensions.
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## See Also
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* [Arrays](Arrays)
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* [DIM](DIM), [SHARED](SHARED)
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* [_PRESERVE](_PRESERVE), [ERASE](ERASE)
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* [$DYNAMIC]($DYNAMIC), [$STATIC]($STATIC)
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