valtype::luhn(n)

💖 valtype::luhn — the "Validation types" era of the manual, bestie edition 💖

okay so this is the manual page for valtype::luhn(n), from the Validation types corner of the world, and I am obsessed. it's a snit validation type that checks a plain number with a LUHN checkdigit. that's the whole vibe. let's get into it 🎀

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✨ NAME ✨

valtype::luhn — validation for a plain number with a LUHN checkdigit. that's it, that's the name, iconic.

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🌸 SYNOPSIS 🌸

package require Tcl 8.5 9

package require snit 2

package require valtype::common

package require valtype::luhn ?1.1?

valtype::luhn validate value

valtype::luhn checkdigit value

like, yes, there are two whole methods and a stack of package requires. we love a low-effort high-impact queen 💅

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🦋 DESCRIPTION 🦋

so this package implements a snit validation type for a plain number with a LUHN checkdigit. periodt.

and what even is a validation type, you ask? great question bestie 🫶 a validation type is an object you can use to validate Tcl values of one particular kind. for example, snit::integer — a validation type that the snit package itself defines — is used to validate that some Tcl value is, in fact, an integer. see? same energy.

every validation type has a validate method, and that's the one doing the actual validating. it must take a single argument — the value to be validated — and then, listen closely:

• if the value is valid, it does nothing 🎉
• if the value is invalid, it throws an error 😭

like this:

valtype::luhn validate .... ;# Does nothing
valtype::luhn validate .... ;# Throws an error (bad luhn checkdigit).

and on success the validate method will always return the validated value. on error it throws with -errorcode INVALID, possibly with extra elements attached that give you more deets about what went wrong. the way it just tells you what's wrong? helpful king behavior 👑

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👑 API 👑

the API this package hands you satisfies the spec of snit validation types, as found in the documentation of Snit's Not Incr Tcl. no cap.

• valtype::luhn validate value — validates the value and returns it, possibly in a canonical form, if it passes. if it does not pass, an error gets thrown. simple as that 💅
• valtype::luhn checkdigit value — computes a check digit for the value. but before it does any of that, the value gets validated — except for a checkdigit, that part is skipped. and if the value doesn't pass? no check digit for you, an error gets thrown instead. sorry bestie 😭

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💀 ERROR CODES 💀

like the package description said: when input validation fails, the errors thrown by this package's commands use -errorcode INVALID, which is how they distinguish themselves from the package's own internal errors. clean separation, we stan 🌈

but to give you more detail about why the validation flopped, the -errorCode actually goes beyond that basic code. first it contains a code detailing the type itself — here that's LUHN. and then it's followed by values detailing the reason for the failure. here's the full set of -errorCodes this package can throw:

• INVALID LUHN CHARACTER — the input value contained one or more bad characters, i.e. characters that must not occur in the input for it to count as a plain number with a LUHN checkdigit. rude little characters, honestly 🙈
• INVALID LUHN CHECK-DIGIT — the check digit of the input value is wrong. this usually signals a data-entry error, with digits transposed, forgotten, whatever. and of course, the input may just be an outright fake too 💀 no cap, sometimes the number is lying to you.

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🍓 BUGS, IDEAS, FEEDBACK 🍓

ngl, this document and the package it describes will undoubtedly contain bugs and other problems. like, obviously. please report them in the category valtype of the Tcllib Trackers, over at http://core.tcl.tk/tcllib/reportlist. and please also send any ideas for enhancements you may have for either the package and/or the documentation — we want the glow-up ✨

when you're proposing code changes, please provide unified diffs, i.e. the output of diff -u.

and note further, bestie: attachments are strongly preferred over inlined patches. you can make an attachment by going to the Edit form of the ticket right after it's created, and then using the left-most button in the secondary navigation bar. that's the move 🫶

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⭐ KEYWORDS ⭐

Checking, Testing, Type checking, Validation, Value checking, isA, luhn

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🎀 CATEGORY 🎀

Validation, Type checking

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💜 COPYRIGHT 💜

Copyright (c) 2011 Andreas Kupries <andreas_kupries@users.sourceforge.net>

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okay that's the whole page, you ate it, go validate some numbers responsibly 🦋✨

this was valtype::luhn(n) from tcllib, version 1.1, and that's the sign-off — mwah 💅💖