Considering
the syntax in detail and the handling of ActionScript, we are going to begin speaking
about **operators**,
because of they are the most elementary part of an ActionScript action (and of many
other programming languages).
An **operator** is a character that does an special action inside an ActionScript expression.
An expression is nothing more as a set of operators, variables and constants related
to each other in a certain way. Flash will take out a result from all the expressions
that finds in our movie. For example:
x
= 3 ; --> It is an expression which results in assigning the value 3 (that's a constant) to the variable
'x'
y
= 5 + x ; --> It is an expression which results will be to assign to the variable
'y' the sum of the constant 5 and the variable 'x' that is equal 3 (because we have
assigned this value to it before). Therefore, the result of this expression is the assignment of the value 8 (3 + 5) to ' y '.
Flash
allows us to use many operators, we are going to comment the most common
of them. The reader can access the others (and these ones) from the **Actions
Panel** in
the folder **Operators**.
We are going to classify the operators as Flash does.
** Arithmetic
Operators **
** +** : **Sum**.
This operator serves, as expected, to add 2 values.
**-** : **Substract **.
It does the operation of subtracting 2 values.
***** : **Multiplication**.
It multiplies 2 values
**/** : **Division**.
It is the classic operation of division. In contrast with some programming languages,
this operator does a complete division (including decimals)
**%** : **Remainder
Operator **.
This operator, not very known in mathematics, is a classic of the programming. It
returns the remainder between 2 numbers. *Example:
4 % 3 = 1, 4 % 2 = 0.*
** Assignment
Operators **
** =** : **Equal**.
This is the most important operator of this category and without doubt, one of the
most used. It stores the value located in the right side of the expression to the
left side. *Ex:
x = 2 + 3. It stores the value of (2 + 3) in the variable x.*
Actually,
the rest of operators of this category are ways to do several operations at
the same time, we'll describe one as example, the others are done exactly in
the same way.
**+=** : **PlusEqual**.
This operator assigns to the expression located on the left of the operator the resulting
value of adding the expression located on the right side with the left side expression. *Example*:
(We suppose that x = 4 e y = 3) then, the expression * x
+= y would cause that x becomes the result of summing (3 + 4).* Therefore,
the expression x += y is equivalent to doing: x = x + y.
** Comparison
Operators**
** ==** : **Verify
Equality **.
This operator serves to verify if 2 expressions are equal. If they are, the value
of the comparison expression is ' true'. By semantic reasons, say that an expression
is true is equivalent to say that it is equal to 1. If they are not equal, it gives
back 'false' or the value 0.
This
possibility of verifying if an expression is equal to another one, will be very useful
to verify many items during our movie and depending on them, doing one or others
things.
We'll
put an example; let's imagine that we ask a user to introduce his age in a text
field of our flash movie. We call this field "age_user". We make him press
a button "Continue" and at this moment we verify his age, if he is 20 years
old, we say something to him, otherwise, we say another different thing to him. It
would be enough to do something like this:
if
(age_user == 20) {
give_message_1;
}
else
{
give_message_2;
}
Here
we are saying the following: "If age_user is equal to 20, then give the
message 1, otherwise, we give the message 2.
We'll
see the meaning of 'if' and ‘else’, so don't be concerned
about not understanding perfectly the code written above. Logically the creation
of the functions "give_message_1" and "give_message_2" is also
compulsory.
**>** : **Greater
than**.
It returns true (1) if the expression from the left is greater than the
one from the right. Otherwise, it returns false (0).
**<** : **Less
than**.
It returns true (1) if the expression from the left is minor to the one
from the right. Otherwise, it returns false (0).
**>=** : **Greater
than or equal **.
It returns true (1) if the expression from the left is greater or equal
to the one from the right. Otherwise, it returns false (0).
**<=** : **Less
than or equal **.
It returns true (1) if the expression from the left is minor or equal
to the one from the right. Otherwise, it returns false (0).
**!=** : **Verify
Inequality **.
It returns true (1) if the expression from the left is different from the
one from the right. Otherwise, it returns false (0). Example: 3 != 4 would result giving a false (0). So 3 are, indeed, different
from 4.
** Other
Operators **
** (
) ** : **Parentheses**.
They serve to group terms and to give preferences in the operations (it is the
same as in mathematics). It is also used, as we already saw, to assign parameters
to functions or to actions. (These must be between parentheses)
** "
"** : **Quotes**.
In ActionScript, all that goes between quotes is considered a string of characters,
so that the functions and actions that affect exclusively to the character strings also
begin to affect a element between quotes. So for example, while x represents a variable
with a determined value, if we write "x", we are writing in fact the character
or letter "x". Therefore, we’ll be able to add it to a word, compare
it with another letters, write it on the screen etc.. but it will never be a variable.
The
rest of operators are not of so wide use, their functionality and definition is explained
in the own Flash help. |