These statements serve to perform different set of statements depending on condition value.
On the basis of the Condition
value, this
statement decides whether the Statement
should be executed.
If the Condition
is true,
the Statement
is executed.
If it is false, the
Statement
is ignored and the process continues next
after the if
statement.
The Statement
is either a simple statement or a block
of statements
if (Condition) Statement
Unlike the previous version of the if
statement (in which the Statement
is
executed only if the Condition
is true), other
Statements
that should be executed even if the
Condition
value is false can be added to the
if
statement.
Thus, if the
Condition
is true,
the Statement1
is executed, if it is false,
the Statement2
is executed. See below:
if (Condition) Statement1 else Statement2
The Statement2
can even be another
if
statement and also with
else
branch:
if (Condition1) Statement1 else if (Condition2) Statement3 else Statement4
Example 64.19. If statement
integer a = 123; if ( a < 0 ) { a = -a; }
Sometimes you would have very complicated statement, if you
created the statement of more branched out if
statement.
In this case, it is much more convenient to use
the switch
statement.
Now, instead of the Condition
as in the if
statement with only two values (true or false),
an Expression
is evaluated and
its value is compared with the Constants
specified in the switch
statement.
Only the Constant
that equals to the value of the Expression
decides which of the Statements
is executed.
If the Expression
value is Constant1
, the Statement1
will be executed, etc.
Important | |
---|---|
Remember that literals must be unique in the |
switch (Expression) { case Constant1 : Statement1 StatementA [break;] case Constant2 : Statement2 StatementB [break;] ... case ConstantN : StatementN StatementW [break;] }
The optional break;
statements ensure
that only the statements corresponding to a constant will be executed.
Otherwise, all below them would be executed as well.
In the following case, even if the value of the
Expression
does not equal the values of the
Constant1,...,ConstantN
,
the default statement (StatementN+1
) is executed.
switch (Expression) { case Constant1 : Statement1 StatementA [break;] case Constant2 : Statement2 StatementB [break;] ... case ConstantN : StatementN StatementW [break;] default : StatementN+1 StatementZ }
Example 64.20. Switch statement
integer ok = 0; switch ( response ) { case "yes": case "ok": a = 1; break; case "no": a = 0; break; default: a = -1; }