simple logic question: check if x is between 2 numbers

问题

I want to see if a variable is between a range of values, for example if x is between 20 and 30 return true.

What's the quickest way to do this (with any C based language)?

It can obviously be done with a for loop:

function inRange(x, lowerbound, upperbound)
{
  for(i = lowerbound; i < upperbound; i++)
  {
    if(x == i) return TRUE;
    else return FALSE;
  }
}
//in the program
if(inRange(x, 20, 30))
   //do stuff

but it's awful tedious to do if(inRange(x, 20, 30)) is there simpler logic than this that doesn't use built in functions?

回答1:

The expression you want is

20 <= x && x <= 30

EDIT:

Or simply put in in a function

function inRange(x, lowerbound, upperbound)
{
  return lowerbound <= x && x <= upperbound;
}

Python has an in operator:

>>> r = range(20, 31)
>>> 19 in r
False
>>> 20 in r
True
>>> 30 in r
True
>>> 31 in r
False

Also in Python, and this is pretty cool -- comparison operators are chained! This is totally unlike C and Java. See http://en.wikipedia.org/wiki/Python_syntax_and_semantics#Comparison_operators

So you can write

low <= x <= high

In Python -10 <= -5 <= -1 is True, but in C it would be false. Try it. :)

回答2:

Why not just x >= lowerbound && x <= upperbound ?

来源：https://stackoverflow.com/questions/7253261/simple-logic-question-check-if-x-is-between-2-numbers