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## Abuse of Parentheses

Notationally, parantheses seem to be very popular. Almost too popular. The following is a collection of all the different notations that I've found paranthesis used for. If you would like to add one, send me a pull request on Github.

Name Usage Locations (non-exhaustive)
Function application The value $f(2)$ is, oddly, ... Mathematics, programming
Precedence $2+(3\cdot5) \neq (2 + 3) \cdot 5$ Mathematics, programming
Parentheticals The man (who wore flannel) began ... Writing
Ideal $(N) := \{kN \mid k \in \mathbb Z\}$ Ring Theory
Tuples $(x,y)=(0.5, 1.7)$ Mathematics, programming
Indexing item = my_list(i) MATLAB
$n$-dimensional sequences Consider the sequence $(a_{ij})$ ... Mathematics
Multiplication $(5)(17) = 85$ Mathematics
S-Expression (f x y z) Lisps
Interval notation ...so for any $x$ in $[0, +\infty)$ we have ... Mathematics
$n$ choose $k$ ${n \choose k} = \frac{n!}{k!(n-k)!}$ Mathematics
Matrices $I_2 := \left( \begin{matrix} 1 & 0 \\ 0 & 1 \end{matrix} \right)$ Mathematics
Greatest common divisor $(a, b) := \mathit{gcd}(a, b)$ Mathematics
Generator expression (f(x) for x in li) Python
Function shorthand (+), (+2), (3*) Haskell
Congruence $5 \equiv 15\ (\text{mod } 10)$ Mathematics
Labels See example (B) or refer back to (II) to... Writing
Unit () Haskell
Enumeration Two things: 1) ...; and 2) ... Writing
Emoticon :)    :(    ;)    :'( Texting
Permutation Cycles $(1 3)(2)(4 6 5)$ Mathematics