Computers can perform more than just mathematical tasks - they are also virtuosos in classical logic. Much as how
arithmetic involves manipulating number with addition, multiplication and such, logic involves manipulating the
values true
and false
using its own operators. Those are not text string - they are values as fundamental as
the natural numbers. In computer science, they are both called Booleans, after the 19th century mathematician
George Boole.
is
is a logical operator. Just as + adds the two numbers on each side of it, is
compares two values on each
side and evaluates to true
or false
depending on whether they're identical. It works equally well with strings,
numbers, Array, and anything else, but beware - the string "2"
is not equal to the number 2.
There are several other logical operators available.
Operator | Purpose | Example |
---|---|---|
is | Evaluates to true if both sides are equal, otherwise false . | $bullets is 5 |
is not | Evaluates to true if both sides are not equal. | $friends is not $enemies |
contains | Evaluates to true if the left side contains the right side. | "Fear" contains "ear" |
is in | Evaluates to true if the right side contains the left side. | "ugh" is in "Through" |
> | Evaluates to true if the left side is greater than the right side. | $money > 3.75 |
>= | Evaluates to true if the left side is greater than or equal to the right side. | $apples >= $carrots + 5 |
< | Evaluates to true if the left side is less than the right side. | $shoes < $people * 2 |
<= | Evaluates to true if the left side is less than or equal to the right side. | 65 <= $age |
and | Evaluates to true if both sides evaluates to true . | $hasFriends and $hasFamily |
or | Evaluates to true if either side is true . | $fruit or $vegetable |
not | Flips a true value to a false value, and vice versa. | not $stabbed |
Conditions can quickly become complicated. The best way to keep things straight is to use parentheses to group things.