b) Instructions
returning a value
************************************
Some instructions return a value. For example, the mathematical
expression "squareroot" returns a number. For example :
hehe = squareroot(4);
The variable "hehe" now contains the value 2.
c) Control
Instructions
*************************
The control instructions are not usually written with parenthesis, if
they dont require parameters.
- repeat
This instruction requires that what is to be repeated is placed
within braces
{}. The parameter is the number of times the instruction is to be
repeated. For example :
hehe = 30;
repeat(20)
{
forward(hehe);
}
is equivalent to:
forward(600);
Note that such an expression cannot be written in the
console, because it will give an error message. You will have
to write it up in a "New function..." window and give it a name.
There is no semi-colon after the braces or after the
instruction "repeat".
You can leave the execution of the instructions within the braces
with the instruction"break", For example:
repeat(20)
{
forward(10);
break;
}
is equivalent to :
forward(10);
The instruction "break" exits the loop. This instruction is
useful when there are many iteration and selection instructions.
There is no parenthesis after the instruction "break".
- the"while"
instruction
This instruction allows you to repeat an instruction as long as a
condition remains true. For example:
hehe = 20;
while (hehe > 0)
{
forward(30);
hehe = hehe -1;
}
is equivalent to :
forward(600);
Within the braces, one can exit the loop immediately with the
"break" instruction. Here again, the elaborate version must be
typed in the "New function..." window.
The condition "hehe > 0" is evaluated at every iteration.
Larger than >
Smaller than <
Equal ==
Different from !=
Larger or equal to >=
Smaller or equal to <=
One can compare numbers with numbers and characters with
characters
-the"if"
instruction
This instruction allows you to make a selection. There is a second
instruction, "else ", which is
optional. It is similar to the while instruction. For example :
hehe = 12;
if (hehe == 12)
{
forward(10);
}
is equivalent to :
forward(10);
We can also write:
hehe = 12;
if (hehe != 12)
{
forward(10);
}
else
{
forward(20);
}
This is equivalent to :
forward(20);
There is no semi-colon after the braces or after the
instructions " if " and " else ".