---
title: "Simplify your code with ad hoc tuples"
url: "https://www.bekk.christmas/post/2020/07/simplify-your-code-with-ad-hoc-tuples"
authors: ["Holger Ludvigsen"]
published: "2020-12-07"
updated: "2024-11-07T13:05:29Z"
language: "en-US"
type: "article"
tags: ["Elm"]
---

# Simplify your code with ad hoc tuples

With Elm's strong types, we must be precise when writing our business code. Precision is a good thing, but it often has the drawback of being verbose. Ad hoc tuples can save the day with clear and precise syntax!

A typical case is when you need to check multiple values. Let's say the user has chosen a size and optional color name for their product:

```elm
type Size
    = Small
    | Large

size : Size
color : Maybe String
```

And we want to put a suitable text in their confirmation dialogue:

```elm
case size of
    Small ->
        case color of
            Just colorName ->
                "A modest " ++ colorName

            Nothing ->
                "Don't worry! We will find a color for you"

    Large ->
        case color of
            Just colorName ->
                "A big great " ++ colorName

            Nothing ->
                "Don't worry! We will find a color for you" -- Oh no, duplication!
```

Instead of indenting away into these nested case-expressions, a common trick is to use an _ad hoc tuple_ combining the two values into `( size, color )`. Notice how clear this make the outcomes of each case:

```elm
case ( size, color ) of
    ( Small, Just colorName ) ->
        "A modest " ++ colorName

    ( Large, Just colorName ) ->
        "A big great " ++ colorName

    ( _ , Nothing ) ->
        "Don't worry! We will find a color for you"
```

Or consider if this `if .. else` expression for the email adress of a fictional company:

```elm
email =
    if (userDepartment == Technology && reportTitle == "Incident") then
        "brent@phoenix.com"

    else if userDepartment == Operations then
        "office@phoenix.com"

    else if (userDepartment == Sales && reportTitle == "Big sales lead") then
        "yuppie@phoenix.com"

    else
        "mail@phoenix.com"
```

This can be more consisely expressed with `case .. of` on a tuple:

```elm
email =
    case (userDepartment, reportTitle) of
        (Technology, "Critical incident") ->
            "brent@phoenix.com"

        (Operations, _) ->
            "office@phoenix.com"

        (Sales, "Big sales lead") ->
            "yuppie@phoenix.com"

        _ ->
            "mail@phoenix.com"
```

## Don't topple the tuple

Before we run off with our newly acquired hammer and see a world of nails, beware that tuples in Elm are intentionally restricted to _maximum three members_.

The reasoning is that if you combine more values than this, you are probably better off with a proper data structure like a record where the fields are named. This is a strong restriction, but all the good kids will get the gift of clean readable code.

## Relevant resources recommended by the author

- [Language Idea: Limit custom types to three arguments](https://dev.to/skinney/language-idea-limit-custom-types-to-three-arguments-27p1)

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