Hi Yesod developers. Attached are two modules to implement CSS size wrappers for Hamlet. It implements several types for different CSS units: * em - EmSize * ex - ExSize * px - PixelSize * % - PercentageSize * cm, in, mm, pc, pt - AbsoluteSize You can create them using an mkSize Template Haskell function, e.g. let size = $(mkSize "100%") All types are instances of Show, Eq, Ord, Num, Fractional and ToCss. This allows you to do math and interpolate it to Hamlet. Ideally, I wanted to have only one type and make an implicit conversion from string literals. But I do not know how to forbid mixing of incompatible units in math (e.g. 10px + 10cm) with a single type. And I do not know how to make implicit conversion from string literals with multiple types. I would appreciate any comments. Including on naming style, type design, API and overall usefulness. Keep in mind that this is the first time I use Template Haskell, so the code may be not optimal and plain ugly (e.g. can we use quasi quotes instead of directly messing with TH?) BTW Michael, one more thing I miss in Hamlet is defining variables in templates. I would prefer to put simple CSS-related constants directly in Cassius instead of a dedicated module. Is it possible to implement? Regards, Dmitry