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+6 votes
in Clojure by

If you have a transducer chain that makes a stream of strings, you might want to accumulate them at the end into a string. Existing functions like str will generate a lot of overhead as there is no stateful accumulator you can maintain.

What you really want is a StringBuilder that accumulates, and emits the string at finalization.

String joining could then be something like:

(transduce (interpose ",") str! coll)

extensible with more transducers as needed.

cgrand's xforms lib has something like this: https://github.com/cgrand/xforms/blob/2079b74271b858b6a91dcb87bc58f3b93ea0b19c/src/net/cgrand/xforms/rfs.cljc#L145-L147

1 Answer

+1 vote