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<div>Hi,</div>
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<div>I tried to define the following function by pattern matching</div>
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<div>codeDouble : ∀{n : ℕ} → Bool × Fin n → Fin (double n)</div>
<div>codeDouble {zero} (b , ())</div>
<div>codeDouble {suc n} (false , zero) = zero</div>
<div>codeDouble {suc n} (true , zero) = suc zero</div>
<div>codeDouble {suc n} (b , suc x) = suc (suc (codeDouble (b , x)) )</div>
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<div>But to my confusion the term "codeDouble {suc n} (b , suc x) “ didn’t reduce. This can be fixed by changing the order</div>
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<div>
<div>codeDouble : ∀{n : ℕ} → Bool × Fin n → Fin (double n)</div>
<div>codeDouble {zero} (b , ())</div>
<div>codeDouble {suc n} (b , suc x) = suc (suc (codeDouble (b , x)) )</div>
<div>codeDouble {suc n} (false , zero) = zero</div>
<div>codeDouble {suc n} (true , zero) = suc zero</div>
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<div>I guess I can answer this myself: since I first match on the boolean agda decides also to do case analysis first on the boolean and then on the Fin which duplicates my last line and has the effect that the defining equality doesn’t hold definitionally
(this is always a bit agda). In this case agda could have matched my definition by changing the order. Is this too much to ask for?</div>
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<div>Cheers,</div>
<div>Thorsten</div>
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