> Hi,
>
> after reading the link and some additional sources, it turns out that a
> valid ISBN-10 has either no separators or four blocks separated by either
> dashes or spaces:
>    Group-Publisher-Title-CheckDigit
>
> Assuming Regex11 (and that I made no mistake), the following should do  
> the
> trick:
>
> IsbnVarifier>>isSyntacticIsbn: aString
>    "no groups"
>    noGrouped := '\d{9}[0-9X]' asRegex.
>    "groups separated by either dashes or spaces"
>    dashes := '\d{1,7}-\d{1,7}-\d{1,7}-[0-9X]'
>    spaces := '\d{1,7} \d{1,7} \d{1,7} [0-9X]'
>    grouped := (dashed , '|' , spaces) asRegex.
>
>    ^(aString matches: nonGrouped) or:
>      [(aString matches: grouped) and:
>        [aString size = 10 + 3]]
>
> Surely, you could cleverly compress the regex even further but that does
> not matter for this example. After checking the syntax, you can just
> iterate over the string and compute the check-digit on the fly.
>
> Kind regards,
> Steffen
>
> Am .09.2020, 18:19 Uhr, schrieb Roelof Wobben via Pharo-users
> <[hidden email]>:
>
>> See here for all the tests :
>> https://github.com/exercism/pharo-smalltalk/blob/master/exercises/isbn-verifier/IsbnVerifierTest.class.st#L88
>>
>> Roelof
>>
>>
>>