gl_gtin - v2.0.0

gl_gtin/check_digit

Check digit calculation module for GTIN codes.

Implements the GS1 Modulo 10 algorithm for calculating and validating GTIN check digits.

Types

CheckDigitError

</>

Error type for check digit operations

pub type CheckDigitError {
  InvalidLength(got: Int)
  InvalidCharacters
}

Constructors 

  • InvalidLength(got: Int)
  • InvalidCharacters

Values

calculate

</> 
pub fn calculate(
  digits: List(Int),
) -> Result(Int, CheckDigitError)

Calculate the check digit for a list of digits.

Implements the GS1 Modulo 10 algorithm:

  1. Multiply digits alternately by 3 and 1 from right to left
  2. Sum all products
  3. Calculate modulo 10 of the sum
  4. If result is 0, check digit is 0; otherwise check digit is (10 - result)

Arguments

  • digits - List of digits (without check digit)

Returns

Ok(check_digit) if successful, Error if the digit list is invalid.

Examples

calculate([6, 2, 9, 1, 0, 4, 1, 5, 0, 0, 2, 1])
// -> Ok(3)

generate

</> 
pub fn generate(code: String) -> Result(String, CheckDigitError)

Generate a complete GTIN with calculated check digit.

Takes an incomplete GTIN (7, 11, 12, or 13 digits) and calculates the check digit to produce a complete GTIN (8, 12, 13, or 14 digits respectively).

Arguments

  • code - Incomplete GTIN string

Returns

Ok(complete_gtin) if successful, Error otherwise.

Examples

generate("629104150021")
// -> Ok("6291041500213")

generate("123456789012")
// -> Ok("1234567890128")
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