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68 lines
2.9 KiB
Plaintext
68 lines
2.9 KiB
Plaintext
A {{KW|REDIM}} statement can re-dimension one [[$DYNAMIC|dynamic]](flexible) [[Arrays|array]] or a [[comma]] separated list of arrays.
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{{PageSyntax}}
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:[[REDIM]] [{{KW|_PRESERVE}}] [{{KW|SHARED}}] ArrayName[''typesuffix''] ({''max_element''|low_element[{{KW|TO}} ''upper_element'', ...]}) [{{KW|AS}} {{KW|TYPE|Type}}]
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{{PageDescription}}
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* Can change the number of elements in an array (the present array data is lost unless [[_PRESERVE]] is used).
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* Dynamic array elements can also be sized or resized by a program user's entry.
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* The [[_PRESERVE]] option also allows the ''element'' range values to be moved upward or downward in '''QB64 only!'''
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* {{Parameter|Array}} is the name of the array to be dimensioned or re-dimensioned.
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* {{Parameter|elements}} is the number of elements the array should hold. Use the optional [[TO]] {{Parameter|elements2}} to set a range.
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* '''Always use the same array [[TYPE]] suffix ([[AS]] type) or a new array type with the same name may be created.'''
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* REDIM cannot change [[$STATIC]] arrays created with a [[DIM]] statement unless the [[$DYNAMIC]] [[Metacommand]] is used!
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* To create a dynamic array use the [[$DYNAMIC]] metacommand or use [[REDIM]] rather than [[DIM]] when first creating the array.
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* 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.
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* '''REDIM [[_PRESERVE]] cannot change the number of array dimensions or type!'''
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* [[$DYNAMIC|Dynamic]] arrays MUST be [[REDIM]]ensioned if [[ERASE]] or [[CLEAR]] are used to clear the arrays as they no longer exist.
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* When [[AS]] is used to declare the type, use [[AS]] to retain that type or it will change to [[SINGLE]]!
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* '''NOTE: Many Qbasic keyword variable names CAN be used with a [[STRING]] suffix($) ONLY! You CANNOT use them without the suffix, use a numerical suffix or use [[DIM]], [[REDIM]], [[_DEFINE]], [[BYVAL]] or [[TYPE]] variable [[AS]] statements!'''
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* '''Warning! Do not use negative array upper bound index values as OS access or "Out of Memory" [[ERROR Codes|errors]] will occur!'''
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''Example 1:'' The [[$DYNAMIC]] Metacommand allows an array to be re-sized using [[DIM]] and REDIM.
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{{CodeStart}} '' ''
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'{{Cl|$DYNAMIC}}
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{{Cl|INPUT}} "Enter array size: ", size
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{{Cl|DIM}} Array(size)
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{{Cl|REDIM}} Array(2 * size)
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{{Cl|PRINT}} {{Cl|UBOUND}}(Array) '' ''
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{{CodeEnd}}
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''Example 2:'' Shows the difference between REDIM and REDIM [[_PRESERVE]].
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{{CodeStart}} '' ''
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{{Cl|REDIM}} array(20)
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array(10) = 24
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{{Cl|PRINT}} array(10)
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{{Cl|REDIM}} {{Cl|_PRESERVE}} array(30)
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{{Cl|PRINT}} array(10)
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{{Cl|REDIM}} array(15)
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{{Cl|PRINT}} array(10) '' ''
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{{CodeEnd}}
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{{OutputStart}}
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24
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24
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0
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{{OutputEnd}}
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: ''Explanation:'' REDIM without _PRESERVE erases the array data and cannot change the number of dimensions.
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{{PageSeeAlso}}
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* [[Arrays]]
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* [[DIM]], [[SHARED]]
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* [[_PRESERVE]], [[ERASE]]
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* [[$DYNAMIC]], [[$STATIC]]
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{{PageNavigation}}
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