Last time we discussed some control structures, today we will discuss switch control structures, assignment and increment decrement operators.
Rvalues and Lvalues:
switch structure tests variable/expression for multiple possible values, a Specific action is to be performed based on the value of an ‘integral expression' (Combination of characters and integers that evaluate to a constant integer value)
Switch statement consists of two parts:
flow chart of a switch selection structure (remember, we select one out of many choices) :
Rvalues and Lvalues:
- Rvalues: these are the expressions that appear on left side of equation, they can be changed (i.e., variables) x = 4;
- Lvalues: these are expressions that appear on right side of equation, they include constants such as numbers (i.e. cannot write 4 = x;)
- Lvalues can be used as Rvalues, but not vice versa.
switch structure tests variable/expression for multiple possible values, a Specific action is to be performed based on the value of an ‘integral expression' (Combination of characters and integers that evaluate to a constant integer value)
Switch statement consists of two parts:
- a controlling expression ie switch (…………)
- and a series of case labels and optional default case, Case labels contain the possible values of the controlling expression
- switch statement compares the value of controlling expression with each case label
flow chart of a switch selection structure (remember, we select one out of many choices) :
the following code example shows the usage of a switch structure:
Output example of this code:
Assignment Operators:
Assignment operators are used for abbreviating assignment expressions
–Addition
assignment operator
c = c + 3;
c += 3;
c += 3;
Statements
of the form
variable = variable operator
expression;
can
be rewritten as
variable operator = expression;
Other
assignment operators are:
d -= 4 (d = d - 4)
e *= 5 (e = e * 5)
f /= 3 (f = f / 3)
g %= 9 (g = g % 9)
Increment and Decrement Operator:
Increment
operator (++) - can be used instead of
c += 1 OR
c = c + 1
Decrement
operator (--) - can be used instead of
c -= 1 OR
c = c - 1
Preincrement:
Whenever the operator is used before the variable (++c or ––c) then first the variable
is changed, then the expression it is in is evaluated.
Postincrement:
Whenever the operator is used after the variable (c++ or c--), the the expression
the variable is in executes, then the variable is changed
for example, If c
= 5,
then
cout << ++c;
c is
changed to 6,
then printed out
cout << c++;
Prints
out 5
(cout
is executed before the increment, c then
becomes 6)
When
variables are not in expression:
then preincrementing
and postincrementing have same effect
++c;
cout << c;
and
c++;
cout << c;
are
the same
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