In this post, we will see Assignment Statements | PPL | Sebesta | Expressions and Assignment Statements | assignment statements, ppl, sebesta, expressions and assignment statements
6. Assignment Statements
Simple Assignments
i. Nearly all programming
languages currently being used use the equal sign for the assignment
operator.
ii. ALGOL 60 and Ada makes
use of := as the assignment operator.
iii. In some languages, such
as Fortran and Ada, an assignment can appear only as a stand-alone statement,
and the destination is restricted to a single variable.
Conditional Targets
Perl allows conditional targets on assignment statements.
For example, consider
($flag ? $count1 : $count2) =
0;
which is equivalent to
if ($flag) {
$count1 = 0;
}
else {
$count2 = 0;
}
Compound Assignment
Operators
The form of assignment that can be abbreviated
with this technique has the destination variable also appearing as the first
operand in the expression on the right side, as in
a = a + b
By Compound Assignment Operator, above statement
is written as follows:
a+=b
It is provided by ALGOL 68, C-based languages, Perl,
JavaScript, Python, and Ruby.
Unary Assignment
Operators
The C-based languages, Perl, and JavaScript include two
special unary arithmetic operators that are actually abbreviated
assignments. They combine increment and decrement operations with assignment.
In the assignment statement
sum = ++ count;
It is similar to
count = count + 1;
sum = count;
If the same operator is used as a postfix operator, as
in
sum = count ++;
It is similar to
sum = count;
count = count + 1;
count ++
It is similar to
count=count+1
When two unary operators apply to the same operand,
the association is right to left. For example, in
- count ++
count is first incremented and then negated. So, it is
equivalent to
- (count ++)
Assignment as an
Expression
Expression is evaluated and then it is assigned.
e.g.
1. while ((ch = getchar()) !=
EOF) { ... }
2. a = b + (c = d / b) - 1
Multiple Assignments
Some programming languages like Perl, Ruby, and Lua
supports multiple-target, multiple-source assignment statements.
For example, in Perl one can
write
($first, $second, $third) = (20, 40, 60);
Here, $first is assigned 20,
$second is assigned 40 and $third is assigned 60.
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