http://paulgraham.com/arcfaq.html

Why not use some other delimiter than parentheses?
为什么不使用一些其他的分隔符比括号？
We tried various possibilities. Square and curly brackets lose because they are less directional than parens (left and right differ in fewer pixels); < and > lose because they don't wrap around enough to enclose expressions longer than tokens.
我们尝试了各种可能性。因为他们比父辈不定向输方括号（左和右在更少的像素不同）；<和>亏损是因为他们不缠绕足以将表达式超过令牌。