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elisp

Convert decimal <-> hex

Given a list of decimal numbers, how can each number be converted to its equivalent hexadecimal value, and vice versa?

For example: 

(convert2hex 255 64 64); -> (FF 40 40)
(convert2dec FF 40 40); -> (255 64 64)

(convert2hex 255 64 64 255 64 64 128)
(convert2dec FF 40 40 FF 40 40 80)
Solution

  • Number to Hex:

    (format "%X" 255) ;; => "FF"

    You can also zero-pad the value with:

    (format "%03X" 255) ;; => "0FF"

    Where the 0 is the character to use for padding and 3 is the number of spaces to pad.

    Hex string to number

    (string-to-number "FF" 16) ;; => 255

    The 16 means "read as base-16."