Logiweb(TM)

7.1.9.3 Septet representation

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In vectors and in many other places in Logiweb, naturals (i.e. natural numbers) are expressed in 'septet representation'. Septet representation is a representation in which naturals are expressed little endian base 128 and in which 128 is added to all bytes except the last.

We shall refer to a natural in the range 0..255 as a 'byte', to a natural in the range 0..127 as an 'end septet', and to a natural in the range 128..255 as a 'middle septet'. In septet representation, a natural is represented by a sequence of zero, one, or more middle septets followed by precisely one end septet.

As an example, the septet sequence

  129 130 131 4

represents the natural

  1+128*(2+128*(3+128*4))=8438017

As another example, the septet sequence

  128 2

represents the natural

  0+128*2=256

As a final example, the septet sequence

  2

represents the natural

  2

In general, naturals in the range 0..127 are represented by themselves.

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Copyright © 2010 Klaus Grue, GRD-2010-01-05