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Elm Complete Course / Custom Types

as patterns

Learn as patterns in Elm with a construct-specific explanation, a unique example, a practical boundary, and a mastery check.

10 min read • Beginner

as patterns is an atomic Elm topic inside Custom Types. The example below uses the actual construct named by the lesson rather than a generic placeholder.

Focus on what as patterns changes: the input, binding, control path, object state, collection, runtime effect, or language contract. Then alter one value and verify that the behavior changes for a reason specific to this feature.

Topic-specific example

elm-03-08-as-patterns.elm
elm Try It Live 
keepPair (( a, b ) as pair) = if a == b then pair else ( b, a )
Edge case / engineering note

Change the key input in this Elm example and predict the result first; the named construct should be the reason the behavior changes.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

as patterns Mastery Check →
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Recursive custom types