Change a Hexadecimal String to a value using the BASIC Function Library.

' Function to convert a HEX number string to a value

' Call: hex_to_val(hex_string, string_size)

' e.g. x = hex_to_val("38E38D", 6)

'

FUNCTION hex_to_val(hex_string AS STRING, str_size AS INTEGER) AS INTEGER

     DIM i, ch_posn, ret_value AS INTEGER

     DIM charstring AS STRING(1)

     ret_value = 0: ch_pos = 0

     FOR i = str_size - 1 TO 0 STEP - 1

         charstring = MID(hex_string, i, 1)

         ret_value = ret_value + char_to_val(charstring, ch_pos)

         ch_pos = ch_pos + 1

     NEXT i

     RETURN ret_value

ENDFUNC

' Function to convert one character to a weighted value

' Character is sent as a single character string

' Returns an integer value that is character_value * 2 ^ character_position

' Call: char_to_val(character_string, position)

' e.g. x = char_to_val("A", 3)

'

' If the ASCII character is not 0..9 or A..F then 0 is returned

' (Upper case letter only)

'

FUNCTION char_to_val(ch AS STRING, posn AS INTEGER) AS INTEGER

     DIM ch_asc, weight AS INTEGER

     weight = 2 ^ (posn * 4)

     ch_asc = ASC(ch)

     IF ch_asc < $3a AND ch_asc > $2F THEN

          RETURN(ch_asc - $30) * weight

     ELSEIF ch_asc < $47 AND ch_asc > $40 THEN

          RETURN(ch_asc - 55) * weight

     ELSE

          RETURN 0

     ENDIF

ENDFUNC

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Here is an example program calling the function:

DIM hexstring AS STRING(10)

DIM x AS INTEGER

hexstring = "01FFFF"

x = hex_to_val(hexstring, 6)

PRINT x