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In category theory, we always use many composition notation. And in computer science, we often use category theory to describe problems.

Usually, we use g ∘ f to stand the composition of "g after f"

Also, we use f ; g to stand the composition of "f before g"

But the ; is a common used syntax of line end in computer program, is there any substitutable notation of ; ?

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    I asked the same question here http://math.stackexchange.com/questions/1982144/is-there-a-commonly-used-notation-for-flipped-composition – 2017-01-06
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    I'm going to suggest people start using $\ggg$ for this. Like in Haskell's control.arrow – 2017-01-06
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    @QthePlatypus In haskell `>>>` is a operator have different infix level with `.`, so I'd like to define a operator `flip (.)` has same infix level with `(.)`, but `;` is not a acceptable char. – 2017-01-06
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    I know a few category theorists (on the computer science side of things) that just unabashedly write $fg$ for the composition of morphisms $f:X \to Y$ and $g:Y \to Z$. – 2017-01-06

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