OpenEuphoria

Re: boolean sequence

• Posted by "Juergen Luethje" <j.lue at gmx.de> Sep 02, 2004
• 564 views

Tone =A6koda wrote:

> in C++ if you have an array of 100 boolean (0 or 1) values it will take
> only 100 bits (the C++ "bitset" class exists), in euphoria same array
> will take 32*100bits, 32x more memory. so if you have very large array,
> there is big difference between 1 MB and 32 MB. 1 MB will quickly
> allocate, 32 MB will take long to allocate.
>
> does in euphoria exist any such library? similar library could exist
> for array with char types (8bit) (0-255 numbers), and array with short
> types (16bit) (0 to 65,535 numbers).
>
> i want such library to save memory and also maybe speed.

In the Euphoria archieves, there is my library "bit.zip".
Besides other routines, it contains 5 functions that let you
treat 32-bit integers as "bit arrays". Short descriptions:

- x = bit_set(x, number)
  Set the bit in 'x', that is indexed by 'number', to 1.

- x = bit_reset(x, number)
  Set the bit in 'x', that is indexed by 'number', to 0.

- i = bit_test(x, number)
  Return the value (0 or 1) of the bit in 'x', that is
  indexed by 'number'.

- i = bit_scan_forward(x)
  Return the number of the lowest order bit in 'x', that is
  set (or return -1, if x = 0).

- i = bit_scan_reverse(x)
  Return the number of the highest order bit in 'x', that is
  set (or return -1, if x = 0).

All these functions are fast, because they are internally
implemented in ASM.

Regards,
   Juergen

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