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0 pointsgloosx1y ago0 comments

This not really correct, the useReducer hook is not some external state which is smuggled in. It is an actual input for the reconciler which defines an output of this component, so it is perfectly functional even by your definition.

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recursive1y ago

The value counter changes in subsequent invocations. Maybe react redefined some standard terminology, but this is really straightforward. If useReducer is not pure, and it's not, any function that calls it is impure.

gloosxOP1y ago

This reducer is certainly pure, you are confusing it with `st => st++`

recursive1y ago

Tell me, what's the value `counter` returned by this "pure" function invocation?

const [counter, tick] = useReducer(st => st + 1, 0)

Answer: It depends. Sometimes 0, sometimes more.

Any function that can return different results for the same inputs is impure. Therefore, `useReducer` is impure. It can return different results for the same input. React may have some alternate definition for "function" or "pure", but these words existed prior to react.

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0 pointsgloosx1y ago0 comments

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recursive1y ago

gloosxOP1y ago

This reducer is certainly pure, you are confusing it with `st => st++`

recursive1y ago

Tell me, what's the value `counter` returned by this "pure" function invocation?

const [counter, tick] = useReducer(st => st + 1, 0)

Answer: It depends. Sometimes 0, sometimes more.

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