## Abuse of Parentheses

Parentheses are used in... many different ways. I thought I'd collect them.

Name Usage Locations (non-exhaustive)
Function application $f(x)$ Mathematics, programming
Precedence $2+(3\cdot5)$ 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 li(i) MATLAB
$n$-dimensional sequences Consider the sequence $(a_{ij})$ ... Mathematics
Multiplication $(5)(17)$ Mathematics
S-Expression (f x y z) Lisps
Interval notation $[2, +\infty)$ Mathematics
$n$ choose $k$ ${n \choose k}$ Mathematics
Matrices $\left( \begin{matrix} 1 & 0 \\ 0 & 1 \end{matrix} \right)$ 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
Emojis :)    :(    ;)    :'( Texting