Re: How to define Hexa decimal sets/Vectors in TLA+

Here's one approach to a Hex module which continually increments then prints out a hex value:

-------------------------------- MODULE Hex --------------------------------

EXTENDS

Naturals,

Sequences,

TLC

VARIABLES

hexValue

HexDigit == 0 .. 15

Hex == Seq(HexDigit)

HexChar ==

<<"0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F">>

RECURSIVE HexToString(_)

HexToString(hex) ==

IF hex = <<>>

THEN ""

ELSE HexChar[Head(hex) + 1] \o HexToString(Tail(hex))

TypeInvariant ==

/\ hexValue \in Hex

Init ==

/\ hexValue = <<0>>

RECURSIVE IncrementedHexValue(_)

IncrementedHexValue(hex) ==

LET

prefix == SubSeq(hex, 1, Len(hex) - 1)

last == hex[Len(hex)]

IF hex = <<>>

THEN <<1>>

ELSE

IF last < 15

THEN Append(prefix, last + 1)

ELSE Append(IncrementedHexValue(prefix), 0)

Increment ==

/\ Print(HexToString(hexValue), TRUE)

/\ hexValue' = IncrementedHexValue(hexValue)

Next ==

\/ Increment

=============================================================================

Another approach is to consider hex values as simple natural numbers, and operate on them as natural numbers. You can then write a function to convert from natural number to hex string representation.

As an aside, this was my first encounter with string manipulation in TLA+ - I wish TLC treated them as sequences!

Andrew

On Monday, April 16, 2018 at 11:08:38 PM UTC-7, knni...@xxxxxxxxx wrote:

Hi All,

Currently, I am working with sets and vectors.
My set and vector contain hexadecimal numbers.
I need to define subsets of a hexadecimal superset and need to perform some set operations on the same.

-Regards Nikhila K N