When learning computer programming, I found it helpful to look at a function like a pencil sharpener. A parameter was a dull pencil, inside processes sharpened and returned a sharp pencil.
我在学编程时，常把程序比作卷笔刀，而把参数比作钝铅笔，经过处理我们就得到尖铅笔了。
2
Sharp knife sheath to protect themselves, it is satisfied with its dull. — Tagore.
刀鞘保护刀的锋利，它自己则满足于它的迟钝。——泰戈尔。
3
Dull tools can be more hazardous than sharp ones, since it takes more force to cut with a dull blade.