ISBN13 check digit: Difference between revisions

{{works with|langur|0.7.1}}

<lang langur>val .isbn13checkdigit = f(.n) {

val .s = replace .n, RE/[\- ]/

matching(re/^[0-9]{13}$/, .s) and

fold(f{+}, map([_, f .d x 3], map(f .c-'0', s2cp .s))) rem 10 == 0

}

val .tests = h{

"978-1734314502": true,

"978-1734314509": false,

"978-1788399081": true,

"978-1788399083": false,

}

for .key in sort(keys .tests) {

val .pass = .isbn13checkdigit(.key)

write .key, ": ", if(.pass: "good"; "bad")

writeln if(.pass == .tests[.key]: ""; " (ISBN-13 CHECK DIGIT TEST FAILED)")

}</lang>