In traditional mathematics, when we post-compose $x$ by $f$ we write $fx$ or $f(x)$, that is we prefix writing things right to left.
I realize some might be used to it, and it is absolutely trivial, but coming from a culture of left to right writing, this confuses me to no end and it badly hurts my senses.
Is there a standard way of writing things down in the correct order ?
On
When dealing with vectors, some people chose to work with row vectors instead of column vectors, which allows you to reverse the order without re-defining things like matrix manipulation. This works because $$ (AB)^T = B^TA^T $$ Thus, if $x$ is a row vector (i.e. $1\times n$ matrix), $A$ is a $n\times m$ matrix and $B$ a $m\times k$ matrix, "$B$ applied to the result of applying $A$ to $x$" is written $$ xAB $$ whereas if you're working with column vectors, $x$ would be a $n\times 1$ matrix, $A$ as $m\times n$ matrix, and $B$ a $k\times m$ matrix, and you'd write $$ BAx $$
For general function, I've seen some authors do the same, especially in computer science papers. One example that I stumbled over recently was dealing with substitution operations defined on a set of terms, and they used $xS$ to denote the result of applying $S$ to $x$. I personally find that rather confusing, though.
My advice would be to try to get used to reading function applications right-to-left instead of trying to invert your own notation. Using a different notation than everybody else would be a constant source of confusion, without any real benefit.
The notation ';' is sometimes used for this: if $f : A \to B$ and $g : B \to C$, we write $f;g$ to denote $g \circ f : A \to C$.
In the book "Categories, Allegories" by Freyd and Scedrov, the authors write $fg$ to denote what is usually written $g \circ f$.