is_valid_isbn_10 {libbib}

Return TRUE if valid ISBN 10

Description

Takes a string representation of an ISBN 10 verifies that it is valid. An ISBN 10 is valid if it is a 10 digit string or a 9 digit string with a terminal "X" AND the check digit matches

Usage

is_valid_isbn_10(x, allow.hyphens = TRUE, lower.x.allowed = TRUE)

Arguments

x

A string of 10 digits or 9 digits with terminal "X"

allow.hyphens

A logical indicating whether the hyphen separator should be allowed (default is TRUE)

lower.x.allowed

A logical indicating whether ISBN 10s with a check digit with a lower-case "x" should be treated as valid (default is TRUE)

Value

Returns TRUE if checks pass, FALSE if not, and NA if NA

Examples

is_valid_isbn_10("012491540X")    # TRUE
is_valid_isbn_10("0-124-91540-X") # TRUE

# vectorized
is_valid_isbn_10(c("012491540X", "9004037812"))      # TRUE FALSE
is_valid_isbn_10(c("012491540X", "hubo un tiempo"))  # TRUE FALSE