cnpj

A tiny Gleam library for creating, parsing, and validating Brazilian CNPJ numbers.

• Create valid CNPJ values from base and branch parts (check digits auto-calculated)
• Parse formatted or unformatted strings safely into an opaque Cnpj type
• Validate using the official modulus 11 algorithm and reject all-same-digit inputs
• Format as XX.XXX.XXX/YYYY-ZZ or as a 14-digit unformatted string

Install

gleam add cnpj@1

Quick start

import cnpj
import gleam/result

// Parse from a formatted string
let parsed = cnpj.from_string("12.345.678/0001-95")
case parsed {
  Ok(doc) -> {
    // Pretty format
    cnpj.to_string(doc)               // "12.345.678/0001-95"
    // Raw 14 digits
    cnpj.to_unformatted_string(doc)   // "12345678000195"
  }
  Error(err) -> {
    // Convert error to a human-readable message if needed
    cnpj.error_to_string(err)
  }
}

// Quick validity check
cnpj.is_valid("12.345.678/0001-95")   // True
cnpj.is_valid("11.111.111/1111-11")   // False

// Build from parts (check digits are computed for you)
let built = cnpj.from_parts("12345678", "0001")
case built {
  Ok(doc) -> cnpj.to_string(doc)               // "12.345.678/0001-95"
  Error(_) -> Nil
}

API

• from_string(cnpj_string: String) -> Result(Cnpj, CnpjError)
  • Accepts formatted (e.g. "11.444.777/0001-61") or unformatted ("11444777000161").
• from_parts(base: String, branch: String) -> Result(Cnpj, CnpjError)
  • Validates an 8-digit base and a 4-digit branch, then computes check digits.
• is_valid(cnpj_string: String) -> Bool
  • Convenience wrapper around from_string.
• to_string(cnpj: Cnpj) -> String
  • Formats as XX.XXX.XXX/YYYY-ZZ.
• to_unformatted_string(cnpj: Cnpj) -> String
  • Returns the raw 14-digit string.
• error_to_string(e: CnpjError) -> String
  • Maps errors like InvalidLength, InvalidFormat, InvalidCheckDigits, AllSameDigits to messages.

See full docs on HexDocs: https://hexdocs.pm/cnpj.

Development

• Run tests

gleam test

• Format code

gleam format

• Build documentation locally

gleam docs build

Notes

• The Cnpj type is opaque. Construct values via the provided functions to ensure validity.
• Inputs with all identical digits (e.g. "11.111.111/1111-11") are rejected.