Remember?
In your tasks, you have used a specific set of functions to control the agent.
move() to move your agent forwardturnLeft() and
turnRight() to turn your agentcanMove() to tell you’re blocked by a
wallvisitedBefore() to tell you if you
have visited a path beforeisExit() which tells you if you have
reached the exitWhy have we just written the functionality like this?
move()
In program code, this is how we call functions. More on that later.
What else do we need?
We need control instructions to control the flow of execution.
Control instructions are core components of
imperative
programming.
In imperative programming, algorithms are
described as a sequence
of commands to be executed.
Your algorithm is a description of how to achieve a certain result.
Imperative programming is a programming paradigm.
That is a high-level way to conceptualize and structure the implementation of a computer program.
In imperative programming, we have
There are also other paradigms:
https://www.getyarn.io/yarn-clip/87e76303-46c4-4cb3-9552-2b5cf2a9b2e7/gif
What kind of control instructions do we need to escape our maze?
To escape our maze, we need to
To decide, we use conditional statements.
If (A) Then
(B)
Else
(C)
End IfA is a Boolean expression. More on that
later.
The Else-part is optional!
To repeat, we use loops, here a condition-controlled loop:
While (A) do
(B)
DoneB is executed and repeated as long as the condition
A holds.
Another variant of this loop called do while loop:
Do
(B)
While (A)It executes B once before checking A the
first time.
To save our state, we need variables and assignments.
Variables are abstract storage locations with a symbolic name.
Variables contain some data or object referred to as a value.
Variables in CS are different from variables in mathematics!
In mathematics, variables refer to something that can be modified.
In computers, variables can actually change their value.
Assignments are the most fundamental construct in imperative programming.
x = 5This assigns the value 5 to a variable named
x.
The value of x can be changed later in the program
through subsequent assignments.
x = 5
# some other stuff
# happening here
x = 7To evaluate our state, we need expressions.
These are syntactic entities that may be evaluated to determine their value.
Example expressions:
x + y
2 * (i + 1)
pow(x,2)Expressions combine values of variables to a new value.
And what are Boolean expressions?
If (A) Then
(B)
End IfBoolean expressions are expressions that evaluate to
either
true or false.
Example Boolean expressions:
x < 5
x >= y
x == y
x != yWrite code using conditionals
Consider variable x:
x smaller than 5? Let the code call
print("smaller") if so.x contain ‘word’? Let the code call
print("x contains 'word'") if so and
print("nope") otherwise.print("adding one!") and increment x
by one as long as x is smaller than 10.Time: 30 minutes
What have you achieved?
IF x<5 THEN
print("smaller")
ENDIFIF x == 'word' THEN
print("x contains 'word'")
ELSE
print("nope")
ENDIFWHILE x < 10 DO
print("adding one!")
x = x+1
DONEWhat does this count-controlled loop do?
for ( i=1; i<=100; i+=1){
print i;
}A brief summary of control flows:
