How to extract bits from a hexadecimal string

[marcboulle]

This discussion stems from the question received in issue #742

I have a string value representing the status of equipment.
It is encoded as a hexadecimal string, and I would like to extract the bits from this representation.
Can I do this using a Khiops dictionary?

[marcboulle]

Khiops dictionaries allow to extract such information using string rules: https://khiops.org/api-docs/kdic/string-rules/

• Use ToUpper to be case-insensitive.
• Use Translate to replace each hexadecimal character into the corresponding binary substring (e.g., "7" -> "0111", "A" -> "1010").
• Finaly, extract each bit from the resulting binary string, using Middle.

Below is an example of a Khiops dictionary that extracts the 8 least significant bits of a hexadecimal string:

Dictionary	Data
{
	Categorical	HexaString		;	
	
	// Convert hexadecimal string into a binary string. Example: "A19" -> "101000011001"
Unused	Categorical	BinaryString = Translate(ToUpper(HexaString), 
                                             VectorC("0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F"),
                                             VectorC("0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", 
                                                     "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111" ));
                                                                                     
        // Extract the 8 least significants bits. Example with "A19": Bit1="1", Bit2="0", Bit3="0", Bit4="1",...                                                                                
	Categorical	Bit1 = Middle(BinaryString, Diff(Length(BinaryString), 0), 1);	
	Categorical	Bit2 = Middle(BinaryString, Diff(Length(BinaryString), 1), 1);	
	Categorical	Bit3 = Middle(BinaryString, Diff(Length(BinaryString), 2), 1);	
	Categorical	Bit4 = Middle(BinaryString, Diff(Length(BinaryString), 3), 1);	
	Categorical	Bit5 = Middle(BinaryString, Diff(Length(BinaryString), 4), 1);	
	Categorical	Bit6 = Middle(BinaryString, Diff(Length(BinaryString), 5), 1);	
	Categorical	Bit7 = Middle(BinaryString, Diff(Length(BinaryString), 6), 1);	
	Categorical	Bit8 = Middle(BinaryString, Diff(Length(BinaryString), 7), 1);	
};