# Taking TTFX seriously: Can we make common packages faster to load and use

**URL:** <https://discourse.julialang.org/t/taking-ttfx-seriously-can-we-make-common-packages-faster-to-load-and-use/74949>\
**Category:** Performance\
**Tags:** ttfp\
**Created:** [January 20, 2022, 5:16pm UTC](https://discourse.julialang.org/t/taking-ttfx-seriously-can-we-make-common-packages-faster-to-load-and-use/74949 "2022-01-20T17:16:03Z")\
**Posts on this page:** 1\
**Showing post:** 15

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**Author:** ![Krastanov](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/krastanov/32/6817_2.png) [@Krastanov](https://discourse.julialang.org/u/Krastanov)\
**Post date:** [January 22, 2022, 5:05pm UTC](https://discourse.julialang.org/t/taking-ttfx-seriously-can-we-make-common-packages-faster-to-load-and-use/74949/15 "2022-01-22T17:05:18Z")

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Exploring the linked issues, led me to a (seemingly esoteric) thing that is being done with kwargs to help with type inference.

Instead of `function f(...; kw::Bool=false)` people seem to be doing `function f(...;kw::Val{T}=Val(false)) where T`.

I think I am seeing things like this in these OrdinaryDiffEq and Polyester changes:

[https://github.com/SciML/OrdinaryDiffEq.jl/pull/1473/files#diff-8ce813ea8d7f370bc91b5ac1526a80f7fd354be769bafdd6b12b7368f3ae90a9L395](https://github.com/SciML/OrdinaryDiffEq.jl/pull/1473/files#diff-8ce813ea8d7f370bc91b5ac1526a80f7fd354be769bafdd6b12b7368f3ae90a9L395)

[https://github.com/JuliaSIMD/Polyester.jl/commit/5e6ae4c2ae009b507bbcf90ff2c2b9b7d5e94559#diff-a523f7f63af3c48f517501d7e392926093393f7d033fb208f477568ec30bec38L72](https://github.com/JuliaSIMD/Polyester.jl/commit/5e6ae4c2ae009b507bbcf90ff2c2b9b7d5e94559#diff-a523f7f63af3c48f517501d7e392926093393f7d033fb208f477568ec30bec38L72)

Why is this necessary? Why is it better than saying the keyword will be of type Bool?

EDIT: discourse seems to be stripping out the anchors from the links above making it difficult to tell which lines I am talking about. Here are the [SciML](https://github.com/SciML/OrdinaryDiffEq.jl/pull/1473/files#diff-8ce813ea8d7f370bc91b5ac1526a80f7fd354be769bafdd6b12b7368f3ae90a9L395) and [Polyester](https://github.com/JuliaSIMD/Polyester.jl/commit/5e6ae4c2ae009b507bbcf90ff2c2b9b7d5e94559#diff-a523f7f63af3c48f517501d7e392926093393f7d033fb208f477568ec30bec38L72) links with anchors.

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