JCL Help:TExprHashContext.Create
JCL Help: TExprHashContext.Create Constructor
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Summary
Creates an instance of THashContext.
Pascal
public constructor Create(ACaseSensitive: Boolean = False; AHashSize: Integer = 127);
Parameters
| Parameters | Description |
| ACaseSensitive: Boolean = False | Whether this context should be case sensitive or not. |
| AHashSize: Integer = 127 | The hash size to pass on to the internal hash map structure. |
Description
This constructs an instance of THashContext. The first parameter indicates case sensitivity; the meaning of the second parameter is slightly more subtle. It tells the context what value to pass on to the internal hash map's constructor. A large value will mean that the context will take up quite a bit of memory even when it is empty (4 bytes are added for every increase of 1 in the hash size). For good performance, the hash should roughly be the expected average amount of items to be held in the hash. The performance degradation for too small hash tables is logarithmic, however, so only in pathalogical cases should this be a concern.
See Also
About
Donator
Barry Kelly
Notes
It is fairly important that the hash size not be an even number; it's best if it is a prime number, although typically a power of 2 minus one does fairly well (e.g. 127, 2047, etc.).
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