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APL Quest: November 2025 Round-up

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Each Monday we share a challenge from APL Quest – a collection of APL problems that test your array-thinking and highlight the expressive power of APL. These were all originally set as problems in Phase 1 of the APL Problem Solving Competition, which ran from 2009-2023. The APL Wiki has more information on APL Quest.

These are the challenges that we shared throughout November – if you missed them, now is your chance to catch up! Follow our social media channels (#APLQuest) to stay up-to-date with our weekly challenges.

2013-5: Identity Crisis

APL Quest Link: APL Quest 2013-5: Identity Crisis

Write a function that produces an n×n identity matrix.

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2013-6: Home On The Range

APL Quest Link: APL Quest 2013-6: Home On The Range

Write a function that returns the magnitude of the range of a numeric array.

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2013-7: Float Your Boat

APL Quest Link: APL Quest 2013-7: Float Your Boat

Write a function that selects the floating point (non-integer) numbers from a numeric vector.

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2013-8: Go Forth And Multiply

APL Quest Link: APL Quest 2013-8: Go Forth And Multiply

Write a function that produces a multiplication table.

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Try them yourself

All problems include sample solutions, explanations, and discussions. Visit APL Quest to browse the full archive.

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