# ANN: Transducers.jl, efficient and composable algorithms for map- and reduce-like operations

**URL:** <https://discourse.julialang.org/t/ann-transducers-jl-efficient-and-composable-algorithms-for-map-and-reduce-like-operations/19159>\
**Category:** Package Announcements\
**Created:** [January 1, 2019, 3:30am UTC](https://discourse.julialang.org/t/ann-transducers-jl-efficient-and-composable-algorithms-for-map-and-reduce-like-operations/19159 "2019-01-01T03:30:43Z")\
**Posts on this page:** 1\
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**Author:** ![tkf](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tkf/32/17635_2.png) [@tkf](https://discourse.julialang.org/u/tkf)\
**Post date:** [January 1, 2019, 9:50pm UTC](https://discourse.julialang.org/t/ann-transducers-jl-efficient-and-composable-algorithms-for-map-and-reduce-like-operations/19159/8 "2019-01-01T21:50:35Z")

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Thanks for bringing up that example. Let me note that the semantics of `map!` for transducers and iterators are bit different. Transducer `Filter` skips the destination elements as well while the iterator version “compress” all the output in a contiguous chunk. A function that does a similar thing in Transducers.jl is `copy!` (we may need `copyto!` which could be more efficient).

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