there is no associative for '++' and '--' operator

There are two major mistakes there.

• You're actually concerned about the order in which the operands of the list operator (,) are evaluated.

• Operand evaluation order has nothing to do with operator associativity (which determines precedence of instances of operators with the same precedence).

While Perl doesn't document its operand evaluation order, it always evaluates operands from left to right for left-associative operators and exponentiation (**), and from right to left for assignments operators.

This case is no exception. There are two characteristics (features?) of Perl that cause the result you observe:

• Perl passes arguments to functions and subs by reference.

• $a, --$a and ++$a return $a as an l-value.

So, that means

printf("%d%d%d%d%d\n",$a++,$a--,++$a,--$a,$a);
[download]

is basically equivalent to

do {
   local @_;
   alias $_[0] = "%d%d%d%d%d\n";
   alias $_[1] = $a++;  # Returns new value 5, $a=6
   alias $_[2] = $a--;  # Returns new value 6, $a=5
   alias $_[3] = ++$a;  # Returns $a (lvalue)  $a=6
   alias $_[4] = --$a;  # Returns $a (lvalue)  $a=5
   alias $_[5] = $a;    # Returns $a (lvalue)  $a=5
   \&printf;
}
[download]

When printf gets the values from @_, it sees

• 5
• 6
• 5 (the current value of $a)
• 5 (the current value of $a)
• 5 (the current value of $a)

When I run the same program in C, I got, 45555. Please explain how it is working?

C leaves the operand evaluation order up to the compiler. Results will vary from compiler to compiler. It looks like yours passed by reference, evaluating from right to left.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.