for example if I have a 2 column layout (main content and a aside) Can I float the main to the left and aside to left/right and then use flexbox to give the aside an equal height compared to the main content?
Do I have to display the whole container to flexbox to include header,main content, aside, and footer or can I just cherry pick one area to use flexbox?
From Overview,
Flex layout is superficially similar to block layout. It lacks many of the more complex text- or document-centric properties that can be used in block layout, such as floats
From Flex Containers,
floatandclearhave no effect on a flex item, and do not take it out-of-flow. However, thefloatproperty can still affect box generation by influencing thedisplayproperty’s computed value.
From Absolutely-Positioned Flex Children,
An absolutely-positioned child of a flex container does not participate in flex layout. However, it does participate in the reordering step (see
order), which has an effect in their painting order.
来源：https://stackoverflow.com/questions/31953105/can-i-use-flexbox-and-float-at-the-same-time-or-use-flexbox-with-absolute-posit