ISBN13 check digit: Difference between revisions

In this example, we map to multiple functions (actually 1 no-op).

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

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

}

In this example, we set a for loop value as it progresses.

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

var .alt = true

for[=0] .d in map(f .c-'0', s2cp .s) { _for += if(.alt=not .alt: .d x 3; .d) } rem 10 == 0

}