Expressions
Why We Need it?
Because some functions will demand from you to put an expression as input like the most useful function $if
What is expression?
Expression is comparing left-side to right-side of it and in middle is an operator that does different action depends on the operator
Left-Side [Operator] Right-Side
The available operators:
| Operator | True when |
|---|---|
| == | left-side equal to right-side |
| != | left-side not equal to right-side |
| > | left-side is greater than right-side (in term of number value) |
| >= | left-side is greater or equal than right-side (in term of number value) |
| < | left-side is less than right-side (in term of number value) |
| <= | left-side is less or equal than right-side (in term of number value) |
| && | left-side is true AND right-side is true |
| || | left-side is true OR right-side is true |
Example Of an expression:
$username==Mido
the left side is $username
the right side is Mido
the operator is ==
Which means this expression will only be true only if Left side and right side are EQUAL
Multiple Expressions
In some cases you will need multiple expressions, in this case you will find && and || useful
Example 1
$username==Mido&&$country==Egypt
This expression above consist of 2 conditions 1- username should be equal to Mido because we used (==)
2- country should be equal to Egypt because we used (==)
3- and both #1 AND #2 should both be true because we used (&&)
Example 2
$username==Mido||$country==Egypt
This expression above consist of 2 conditions 1- username should be equal to Mido because we used (==)
2- country should be equal to Egypt because we used (==)
3- #1 OR #2 should be true because we used (||)
Grouping Expressions
In rare cases, we want to group 2 conditions or more together using (CONDITIONS) to be evaluated first before the others It's same as: 5*4+1 will be 21 and 5*(4+1) will be 25, because grouping gives priority in evalution
We used same technique but in conditions
Example 1
($username==Mido&&$country==Egypt)||($username==Rake&&country==Germany)
This expression consist of 4 different conditions 1- username should be equal to Mido and country should be equal to Egypt
2- username should be equal to Rake and country should be equal to Germany
3- #1 OR #2 should be true for this expression to be true
Example 2
$username==Mido||($country==Egypt||$country==Masr)
This expression consist of 3 different conditions: 1- username should be equal to Mido
2- country should be equal to Egypt or Masr
3- #1 OR #2 should be true