On Mon, 14 Aug 2017, Drew Adams wrote:

>> One point of this library is the convenience of not having to
>> know anything about neither calculator.el nor calc.el to get
>> the answer with easy.
>>
>> Every Emacs user will understand the following:
>> M-x nbc-hex2dec ff RET
>> "ff hexadecimal = 255 decimal"
>>
>> M-: (nbc-oct2dec "644") RET
>> => 420
>>
>> ;; Or just `hex2dec' and `oct2dec' if you customize
>> ;; `nbc-define-aliases' to non-nil.
>
> (format "%d" #xff)  ; hex to decimal
> --> "255"
>
> (format "%x" 255)   ; decimal to hex
> --> "ff"
>
> (format "%d" #o644) ; octal to decimal
> --> "420"
>
> (format "%o" 420)   ; decimal to octal
> --> "644"
For an user familiar with the Emacs '#' read syntaxis might be OK.
But for the average user, it's better to accept more input formats:
(nbc-hex2dec "#xff")
"255"
(nbc-hex2dec "ff")
"255"
(nbc-hex2dec "0xff")
"255"



> And didn't Pascal B. point this out in the thread previously cited?
>
>    (format "#8r%o #10r%d #16r%x" 42 42 42)
>    --> "#8r52 #10r42 #16r2a"

*) cannot be called interactively.
*) This covers the base range 2 <= b <= 16.  Even worse, it silently
    returns a wrong result for b > 16:
(format "#16r%x" 42)
"#16r2a"
(format "#17r%x" 42)
"#17r2a"
(format "#37r%x" 42)
"#37r2a"

Compare with:

(nbc-number-base-converter "42" 10 16)
"2A"
(nbc-number-base-converter "42" 10 17)
"28"
(nbc-number-base-converter "42" 10 37)
;; Signal error: Base ‘b’ must satisfy 2 <= b <= 36: base-in ‘10’ base-out 
‘37’