MATLAB Programming

3 Basic Program Components
Operator
(?(cond)expr)
(?(cond)expr 1
|expr 2
)
Usage
If condition cond is true, then match expression
expr
If condition cond is true, then match expression
expr 1
. Otherwise match expression expr 2
The first entry in this table is the same as an if-then statement. MATLAB
tests the state of condition cond and then matches expression expr only if
the condition was found to be true. In the form of an if-then statement, it
would look like this:
if cond then expr
The second entry in the table is the same as an if-then-else statement.
If the condition is true, MATLAB matches expr 1
; if false, it matches expr 2
instead. This syntax is equivalent to the following programming statement:
if cond then expr1 else expr2
The condition cond in either of these syntaxes can be any one of the following:
• A specific token, identified by either number or name, is located in the
input string. See “Conditions Based on Tokens” on page 3-56, below.
• A lookaround operation results in a match. See “Conditions Based on a
Lookaround Match” on page 3-58, below.
• A dynamic expression of the form (?@cmd) returns a nonzero numeric
value. See “Conditions Based on Return Values” on page 3-58, below.
Conditions Based on Tokens
In a conditional expression, MATLAB matches the expression only if the
condition associated with it is met. If the condition is based on a token,
then the condition is met if MATLAB matches more than one character for
the token in the input string.
Tospecifyatokeninacondition,useeitherthetokennumberor,fortokens
that you have assigned a name to, its name. Token numbers are determined
by the order in which they appear in an expression. For example, if you
3-56