what does two semicolns ';;' do

[larry]

I am looking at some code which process an uploaded file and it has
loops like:

for(;;){ // for([two semicolons){

what is the function of the two semicolons? loop until break?

I've tried to google it but the text filter seems to remove the
semicolons.

[=?UTF-8?B?SXbDoW4gU8OhbmNoZXogT3J0ZWdh?=]

la***@portcommo dore.com wrote:

for(;;){ // for([two semicolons){

what is the function of the two semicolons? loop until break?

The two semicolons are *part* of the "for" construct. See any books on C or
C++ about "for" loops.

That means that the initial statement, the break condition and the loop
statement in that loop are the empty statement.

That means that the for loop does not initialize anything when starting,
does not check for any break condition, and does not perform anything at
the end of each loop.

Which means, that's an infinite loop (until it's broken by calling the
break() construct inside the loop)

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Iván Sánchez Ortega -ivansanchez-algarroba-escomposlinux-punto-org-

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[Jerry Stuckle]

la***@portcommo dore.com wrote:

I am looking at some code which process an uploaded file and it has
loops like:

for(;;){ // for([two semicolons){

what is the function of the two semicolons? loop until break?

I've tried to google it but the text filter seems to remove the
semicolons.

Look up a for loop in the PHP doc. Three expressions, separated by
semicolons. In this case, the expressions are null (which is also valid).

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Jerry Stuckle
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[jmark]

On Jun 28, 1:43*pm, la...@portcommo dore.com wrote:

I am looking at some code which process an uploaded file and it has
loops like:

for(;;){ * * // for([two semicolons){

what is the function of the two semicolons? *loop until break?

I've tried to google it but the text filter seems to remove the
semicolons.

yes, that's an infinite loop

[jimp]

la***@portcommo dore.com wrote:

I am looking at some code which process an uploaded file and it has
loops like:

for(;;){ // for([two semicolons){

what is the function of the two semicolons? loop until break?

Yeah, same as while (1) {.

AIR for(;;) is slightly more efficient/faster than while(1).
--
Jim Pennino

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[larry]

I figured that out soon after I posted it, not very apparent what it
it does though.

Thanks

[sheldonlg]

la***@portcommo dore.com wrote:

I figured that out soon after I posted it, not very apparent what it
it does though.

Thanks

Au contraire! It was **immediately** apparent to anyone who has done
any C, C++, Java, etc. coding.

[Thomas Mlynarczyk]

ji**@specsol.sp am.sux.com schrieb:

AIR for(;;) is slightly more efficient/faster than while(1).

How come? Isn't

for ( init; cond; after ) { stuff }

just syntactic sugar for

init; while ( cond ) { stuff; after }

and should therefore internally be the same?

Greetings,
Thomas
--
Ce n'est pas parce qu'ils sont nombreux à avoir tort qu'ils ont raison!
(Coluche)

[=?UTF-8?B?SXbDoW4gU8OhbmNoZXogT3J0ZWdh?=]

Thomas Mlynarczyk wrote:

ji**@specsol.sp am.sux.com schrieb:

>AIR for(;;) is slightly more efficient/faster than while(1).

How come? Isn't [for] just syntactic sugar for [while] and should
therefore internally be the same?

It really depends on how your compiler optimizes jumps and boolean
expressions. A good compiler will know that both while(1) and for(;;) are
infinite loops and will translate them to non-conditional jumps in
assembler, effectively rendering them the same.

A bad compiler won't.

--
----------------------------------
Iván Sánchez Ortega -ivansanchez-algarroba-escomposlinux-punto-org-

Cristo ha muerto por nuestros pecados, asÃ* que no vamos a frustrarle.

[jimp]

Iv??n S??nchez Ortega <[e-mail]:

Thomas Mlynarczyk wrote:

ji**@specsol.sp am.sux.com schrieb:

AIR for(;;) is slightly more efficient/faster than while(1).

How come? Isn't [for] just syntactic sugar for [while] and should
therefore internally be the same?

It really depends on how your compiler optimizes jumps and boolean
expressions. A good compiler will know that both while(1) and for(;;) are
infinite loops and will translate them to non-conditional jumps in
assembler, effectively rendering them the same.

A bad compiler won't.

And some compilers will recognize one but not the other.
--
Jim Pennino

Remove .spam.sux to reply.