# Commit 2021-08-18 18:52 0d59511a

View on Github →feat(topology/{continuous_function/bounded, metric_space/algebra}): new mixin classes (#8580)
This PR defines mixin classes `has_lipschitz_add`

and `has_bounded_smul`

which are designed to abstract algebraic properties of metric spaces shared by normed groups/fields/modules and by `ℝ≥0`

.
This permits the bounded continuous functions `α →ᵇ ℝ≥0`

to be naturally a topological (ℝ≥0)-module, by a generalization of the proof previously written for normed groups/fields/modules.
Frankly, these typeclasses are a bit ad hoc -- but it all seems to work!