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for/hash
Learn for/hash in Racket with a construct-specific explanation, unique example, engineering boundary, and mastery check.
for/hash is a focused Racket topic inside Collections. This lesson explains the construct itself, the state or value it operates on, and the observable result it produces.
Read the example as a small executable experiment. Identify the exact syntax that belongs to for/hash, then change one input and predict the result before running it.
Topic-specific example
(for/hash ([x (in-range 1 4)]) (values x (* x x)))
for/hash has rules that are easy to miss when the example is copied mechanically. Check the feature-specific boundary shown by this construct: scope, mutability, evaluation order, type constraints, lifetime, error behavior, compile-time restrictions, or resource cleanup where applicable.