Re: [PHP] Re: Switch - Case Statement Questions
On 11/16/2012 8:33 PM, Iñigo Medina wrote:
On Fri, 16 Nov 2012, Jim Giner wrote:
On 11/16/2012 12:38 PM, Tim Streater wrote:
On 16 Nov 2012 at 12:10, Omar Muhsin mrfroa...@gmail.com wrote:
Hello,
I was just wondering after writting the code in version 2 here
below, it turns
out in testing that it actually PHP is not validating the
expressions instead
always I get the first case.
1.Using nested if statement {THE INTENDED BEHAVIOR}:
if ($count 14)
$boxes = 3;
elseif($count 7 $count = 14)
You don't need the count=14 part as you will *only* get there if
$count=14.
$boxes = 2;
else
$boxes = 1;
2. Using Switch {ALWAYS FIRST CASE!!!}
//$boxes = 1;
//switch ($count) {
//case ($count 14):
//$boxes = 3;
//break;
//case ($count 7 $count = 14):
//$boxes = 2;
//break;
//case ($count = 7):
//default :
//$boxes = 1;
//break;
//}
Does anyone know the answer why using the Switch it always execute
the first
case ?
As has been pointed out you need switch(true).
That's a strange way of writing a switch, IMO. You should be using
the if version.
--
Cheers -- Tim
Maybe I'm way out of touch, but when I look at php.net for the syntax
of the switch statement I see:
switch($var){
case (value):
(do something)
case (other value):
(do something else)
}
IN your example, you are using a switch syntax that is nothing like
that. I think that your case statements are not actually
evaluating the value of $count, but are themselves evaluating to a
true value that has nothing to do with $count.
That `switch` is evaluating to true each case. It's an alternative of using
if-elseif structure.
iñ
Here's the manual reference:
http://us.php.net/manual/en/control-structures.switch.php
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My point was that the OP is using a widely different syntax for a Switch
statement, one that I don't understand at all. According to the Manual
his statement should be:
//switch ($count) {
//case ( 14):
//$boxes = 3;
//break;
//case ( 7):
//$boxes = 2;
//break;
//default :
//$boxes = 1;
//break;
//}
To answer Iñigo's comment - the OP's version is very much like an
If-ElseIF structure, and nothing like a Switch.
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Re: [PHP] Re: Switch - Case Statement Questions
On 19 Nov 2012, at 19:35, Tim Streater t...@clothears.org.uk wrote:
On 18 Nov 2012 at 14:44, Jim Giner jim.gi...@albanyhandball.com wrote:
2. Using Switch {ALWAYS FIRST CASE!!!}
//$boxes = 1;
//switch ($count) {
//case ($count 14):
//$boxes = 3;
//break;
//case ($count 7 $count = 14):
//$boxes = 2;
//break;
//case ($count = 7):
//default :
//$boxes = 1;
//break;
//}
To answer Iñigo's comment - the OP's version is very much like an
If-ElseIF structure, and nothing like a Switch.
Just so. Perhaps those who are not grasping the point could re-read their
copy of The Elements of Programming Style by Kernighan and Plauger where
this sort of issue is covered.
And of course, nothing is allowed to have changed since 1978! Using a switch in
that manner is normal for me. Should I change my style simply because you don't
agree with it? If so, why don't you change your style because I don't agree
with that? Code is art; there is no right way to do it. Can code be shown to
be more efficient, elegant, faster, cleaner? Yes. Right or wrong? No.
See, it's all about expectations. When I worked at SLAC, there was a wise guy
there who had removed the catalytic converter from his Scirocco and who
though it clever to race up 280 from San Jose to SLAC at 100mph, sometimes
slipstreaming behind another idiot doing the same. If I look in my rear-view
mirror, I expect those I can see to be doing 70mph tops (that's what a lot of
people did 30 years ago on 280), not 100, and to make judgements accordingly.
Equally, I have certain expectations when I see a switch statement; it trying
hard to look like if-elseif-etc is not one of them.
Why is it their fault for doing 100mph and not yours for assuming they're only
doing 70mph? I'm not saying they're right to be doing 100mph, but I'm
definitely saying you're wrong for assuming they're only doing 70mph.
Assumptions are the mother of all f*** ups.
-Stuart
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3ft9 Ltd
http://3ft9.com/
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Re: [PHP] Re: Switch - Case Statement Questions
2012/11/19 Tim Streater t...@clothears.org.uk
On 18 Nov 2012 at 14:44, Jim Giner jim.gi...@albanyhandball.com wrote:
2. Using Switch {ALWAYS FIRST CASE!!!}
//$boxes = 1;
//switch ($count) {
//case ($count 14):
//$boxes = 3;
//break;
//case ($count 7 $count = 14):
//$boxes = 2;
//break;
//case ($count = 7):
//default :
//$boxes = 1;
//break;
//}
To answer Iñigo's comment - the OP's version is very much like an
If-ElseIF structure, and nothing like a Switch.
Just so. Perhaps those who are not grasping the point could re-read their
copy of The Elements of Programming Style by Kernighan and Plauger where
this sort of issue is covered.
See, it's all about expectations. When I worked at SLAC, there was a wise
guy there who had removed the catalytic converter from his Scirocco and who
though it clever to race up 280 from San Jose to SLAC at 100mph, sometimes
slipstreaming behind another idiot doing the same. If I look in my
rear-view mirror, I expect those I can see to be doing 70mph tops (that's
what a lot of people did 30 years ago on 280), not 100, and to make
judgements accordingly. Equally, I have certain expectations when I see a
switch statement; it trying hard to look like if-elseif-etc is not one of
them.
Just a minor rewrite of the original solution
switch (true) {
case $count = 7:
$boxes = 1;
break;
case $count = 14:
$boxes = 2;
break;
default:
$boxes = 3;
break;
}
Now -- the idea of switch as select on of some similar cases in mind:
Is this really breaking any expectation? I think this one is a valid
example, when switch(true) doesn't break the semantic of the
switch-statement.
And if this is already the end of expectations, then (sorry for that) the
expectations are maybe slightly limited :X I don't say please use
switch(true) wherever possible, but this one is nearly a prototype of a
valid use-case: You have several cases all depending on a single state (the
variable) and all of the same kind = constant.
Beside, because it is so extremely simple example, it can become even more
obvious
switch (true) {
case $count = 7: $boxes = 1; break;
case $count = 14: $boxes = 2; break;
default: $boxes = 3; break;
}
Guess some may argue about coding styles now, but thats not the questios
here (and anyway: Even coding styles could/should be broken, if it leads to
better code. Use it wisely ;)). And now: This _can_ break any expectation?
By the way, your car-expectation sounds dangerous...
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Re: [PHP] Re: Switch - Case Statement Questions
On Sat, Nov 17, 2012 at 4:13 PM, Sebastian Krebs krebs@gmail.com wrote:
2012/11/17 Andrew Ballard aball...@gmail.com
On Nov 16, 2012 10:24 PM, tamouse mailing lists tamouse.li...@gmail.com
wrote:
On Fri, Nov 16, 2012 at 12:41 PM, Sebastian Krebs krebs@gmail.com
wrote:
Beside this it can be rewritten as
switch ((int) (($count-1) / 7) {
case 0: // 1-7
case 1: // 8 - 14
default: // above 15
}
Nice code refactoring :) Just a tad obscure for someone coming along
later
Not only obscure, but depending on the rule being processed could be plain
wrong. It works for the values shown so far, but what if another test is
added to the use case in the future that doesn't fit the clever solution?
Like so often in our developers world many things breaks, when it comes to
new requirements.
Without knowing the intent of the code, it could be a headache to maintain.
Interesting, that you see 5 lines of code and assume, that nobody will ever
get the intent of this code ;) Of course the context is missing. I guess,
that $count is something like remaining days, or such, because 7 and
14 look like one week and two weeks, respectively. Thus I wouldn't
name the variable $count [1], but $remainingDays and voila: Context is
back and so is the intent :)
Of course the above code has a quite limited use-case, but that was the
requirement (for now, see KISS). If you need more, refactor/rewrite it.
That's precisely my point. If the solution you posted, complete with
your assumptions about the significance of the values 7 and 14,
matches the requirements then use it. If your assumptions were wrong,
and a future revision may potentially require special handling for
certain values like 3 or 8 that cannot be evaluated using your
equation, then the whole block may have to be refactored rather than
simply adding a couple lines for the case. In the spirit of keeping
it simple, I would prefer the code that requires less refactoring.
I'm not assuming that nobody will ever get the [coder's] intent of a
segment of code at all. It's not so much about what the code does, as
WHY it is doing it.
[1] Even further: I was taught, that if I ever want to name a variable like
count, status, type, ... I should stop and probably don't use this
name. In most cases they are used wrong. This example here is quite good:
$count what?
It depends. Generally I agree with you, but if it is a simple loop
counter in a small block of code where variable scope issues and
overall readability of the code is not diminished I'm fine with names
like $count or $n.
Andrew
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Re: [PHP] Re: Switch - Case Statement Questions
On 17 Nov 2012, at 10:53, Tim Streater t...@clothears.org.uk wrote:
On 17 Nov 2012 at 01:33, Iñigo Medina imed...@grosshat.com wrote:
On Fri, 16 Nov 2012, Jim Giner wrote:
Maybe I'm way out of touch, but when I look at php.net for the syntax of the
switch statement I see:
switch($var){
case (value):
(do something)
case (other value):
(do something else)
}
IN your example, you are using a switch syntax that is nothing like that. I
think that your case statements are not actually evaluating the value of
$count, but are themselves evaluating to a true value that has nothing to do
with $count.
That `switch` is evaluating to true each case. It's an alternative of using
if-elseif structure.
It may be an alternative, but it breaks the principle of least surprise. If
I'm looking through someone's code, and I see a switch, I expect to see it
used as Jim described. If the writer needs a different type of logic to make
a decision, that is what the cascaded if-elseif-elseif construct is for, when
the tests don't fall into a simple set-of-values choice.
I don't see how it breaks the principle of least surprise (which is a new one
on me. KISS, yes. Least surprise? Wassat?). If you consider that behaviour to
be surprising the don't ever go near Perl.
A switch statement is basically saying take this value and compare it to each
case below in the order they're presented until one matches, then execute that
block of code until you hit a break which will jump execution out of the switch
statement. I don't see how making this value true or false makes it any more
surprising than if it's squirlookle.
The job of a programmer is not to be clever with a view to impress those
who follow, but to achieve the desired outcome while at the same time making
life easy for those who follow.
I don't consider that usage of the switch statement to be clever. It's a
valid usage of the statement which gives it a lot more power. Specifically the
ability to have the code for a given case deliberately fall through to the next
case block is worth any price of admission. And finally, in my opinion, it's
far cleaner than a succession of if/elseif/else statements, and ultimately gets
compiled to very similar opcodes.
I agree that the job of a programmer is to balance providing a fast, efficient,
correct solution and minimising maintenance issues. I see neither side being
compromised by using a switch statement in this manner, in fact I see both
sides potentially getting a boost. Just because the usage is unfamiliar or even
surprising to you doesn't mean it's wrong.
-Stuart
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3ft9 Ltd
http://3ft9.com/
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Re: [PHP] Re: Switch - Case Statement Questions
On Nov 16, 2012 10:24 PM, tamouse mailing lists tamouse.li...@gmail.com
wrote:
On Fri, Nov 16, 2012 at 12:41 PM, Sebastian Krebs krebs@gmail.com
wrote:
Beside this it can be rewritten as
switch ((int) (($count-1) / 7) {
case 0: // 1-7
case 1: // 8 - 14
default: // above 15
}
Nice code refactoring :) Just a tad obscure for someone coming along
later
Not only obscure, but depending on the rule being processed could be plain
wrong. It works for the values shown so far, but what if another test is
added to the use case in the future that doesn't fit the clever solution?
Without knowing the intent of the code, it could be a headache to maintain.
Just my 2 cents.
Andrew
Re: [PHP] Re: Switch - Case Statement Questions
2012/11/17 Tim Streater t...@clothears.org.uk
On 17 Nov 2012 at 01:33, Iñigo Medina imed...@grosshat.com wrote:
On Fri, 16 Nov 2012, Jim Giner wrote:
Maybe I'm way out of touch, but when I look at php.net for the syntax
of the
switch statement I see:
switch($var){
case (value):
(do something)
case (other value):
(do something else)
}
IN your example, you are using a switch syntax that is nothing like
that. I
think that your case statements are not actually evaluating the
value of
$count, but are themselves evaluating to a true value that has nothing
to do
with $count.
That `switch` is evaluating to true each case. It's an alternative of
using
if-elseif structure.
It may be an alternative, but it breaks the principle of least surprise.
If I'm looking through someone's code, and I see a switch, I expect to see
it used as Jim described. If the writer needs a different type of logic to
make a decision, that is what the cascaded if-elseif-elseif construct is
for, when the tests don't fall into a simple set-of-values choice.
But switch(true) is not a surprise by itself, it becomes to, when the
cases are surprising. And the given example directly fall into a simple
set-of-values choice, but the problem is, that switch(val) by design only
covers equality == and thats what this case is: A set like (1) between 1
and 7, (2) between 8 and 14, (Default) greater than 14. On the other side
a looong if-elseif*-else-chain is often more confusing and needs
refactoring anyway.
(Beside: Was the principle of least surprise not a ruby-thing? ;))
The job of a programmer is not to be clever with a view to impress those
who follow, but to achieve the desired outcome while at the same time
making life easy for those who follow.
I don't see a problem in case ($count = 7) or case ($count = 14) or case
($count 14)? I think a developer (or maybe programmer) doesn't need to
be very clever to get the idea behind this.
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Re: [PHP] Re: Switch - Case Statement Questions
2012/11/17 Andrew Ballard aball...@gmail.com
On Nov 16, 2012 10:24 PM, tamouse mailing lists tamouse.li...@gmail.com
wrote:
On Fri, Nov 16, 2012 at 12:41 PM, Sebastian Krebs krebs@gmail.com
wrote:
Beside this it can be rewritten as
switch ((int) (($count-1) / 7) {
case 0: // 1-7
case 1: // 8 - 14
default: // above 15
}
Nice code refactoring :) Just a tad obscure for someone coming along
later
Not only obscure, but depending on the rule being processed could be plain
wrong. It works for the values shown so far, but what if another test is
added to the use case in the future that doesn't fit the clever solution?
Like so often in our developers world many things breaks, when it comes to
new requirements.
Without knowing the intent of the code, it could be a headache to maintain.
Interesting, that you see 5 lines of code and assume, that nobody will ever
get the intent of this code ;) Of course the context is missing. I guess,
that $count is something like remaining days, or such, because 7 and
14 look like one week and two weeks, respectively. Thus I wouldn't
name the variable $count [1], but $remainingDays and voila: Context is
back and so is the intent :)
Of course the above code has a quite limited use-case, but that was the
requirement (for now, see KISS). If you need more, refactor/rewrite it.
[1] Even further: I was taught, that if I ever want to name a variable like
count, status, type, ... I should stop and probably don't use this
name. In most cases they are used wrong. This example here is quite good:
$count what?
Just my 2 cents.
Andrew
--
github.com/KingCrunch
Re: [PHP] Re: Switch - Case Statement Questions
On Sat, Nov 17, 2012 at 3:13 PM, Sebastian Krebs krebs@gmail.com wrote: 2012/11/17 Andrew Ballard aball...@gmail.com On Nov 16, 2012 10:24 PM, tamouse mailing lists tamouse.li...@gmail.com wrote: Just a tad obscure for someone coming along later Without knowing the intent of the code, it could be a headache to maintain. Interesting, that you see 5 lines of code and assume, that nobody will ever get the intent of this code ;) Of course the context is missing. I guess, that $count is something like remaining days, or such, because 7 and 14 look like one week and two weeks, respectively. Thus I wouldn't name the variable $count [1], but $remainingDays and voila: Context is back and so is the intent :) This was actually the thrust of my remark about obscurity. I could easily see how the refactored algorithm worked from the original code's algorithm. What was obscure was exactly the variable name $count, i.e., the meaning of the data driving the algorithm. When you know the actual meaning of data being used, the obscurity goes away. Hence: useful variable names. Again, well done, Seb. -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Re: Switch - Case Statement Questions
On Sat, Nov 17, 2012 at 2:59 PM, Sebastian Krebs krebs@gmail.com wrote: (Beside: Was the principle of least surprise not a ruby-thing? ;)) No, but the Ruby (and Rails) world takes concepts like this and really runs with them. Principle of Least Astonishment has been around for quite some time, with examples known in software engineering, user interface design, and even real-world objects, It's been in the Patterns wiki for ages: http://c2.com/cgi/wiki?PrincipleOfLeastAstonishment . -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Re: Switch - Case Statement Questions
2012/11/16 Tim Streater t...@clothears.org.uk
On 16 Nov 2012 at 12:10, Omar Muhsin mrfroa...@gmail.com wrote:
Hello,
I was just wondering after writting the code in version 2 here below, it
turns
out in testing that it actually PHP is not validating the expressions
instead
always I get the first case.
1.Using nested if statement {THE INTENDED BEHAVIOR}:
if ($count 14)
$boxes = 3;
elseif($count 7 $count = 14)
You don't need the count=14 part as you will *only* get there if
$count=14.
$boxes = 2;
else
$boxes = 1;
2. Using Switch {ALWAYS FIRST CASE!!!}
//$boxes = 1;
//switch ($count) {
//case ($count 14):
//$boxes = 3;
//break;
//case ($count 7 $count = 14):
//$boxes = 2;
//break;
//case ($count = 7):
//default :
//$boxes = 1;
//break;
//}
Does anyone know the answer why using the Switch it always execute the
first
case ?
As has been pointed out you need switch(true).
That's a strange way of writing a switch, IMO. You should be using the if
version.
Hi,
I've seen long discussions about this ;) I think this one is a example,
where 'switch(true)' is a legit expression, because switch-statements
define a construct, where the interpreter should select one of multiple
similar cases. This one seems legit, because they are very similar ;) It
says In case of $count look like X do this, or $count look like Y do that,
or $count look like Z do something else (and so on). For such I find the
if-elseif-elseif-elseif-elseif-else-construction quite confusing.
Beside this it can be rewritten as
switch ((int) (($count-1) / 7) {
case 0: // 1-7
case 1: // 8 - 14
default: // above 15
}
Regards,
Sebastian
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Re: [PHP] Re: Switch - Case Statement Questions
On Fri, 16 Nov 2012, Jim Giner wrote:
On 11/16/2012 12:38 PM, Tim Streater wrote:
On 16 Nov 2012 at 12:10, Omar Muhsin mrfroa...@gmail.com wrote:
Hello,
I was just wondering after writting the code in version 2 here below, it
turns
out in testing that it actually PHP is not validating the expressions
instead
always I get the first case.
1.Using nested if statement {THE INTENDED BEHAVIOR}:
if ($count 14)
$boxes = 3;
elseif($count 7 $count = 14)
You don't need the count=14 part as you will *only* get there if
$count=14.
$boxes = 2;
else
$boxes = 1;
2. Using Switch {ALWAYS FIRST CASE!!!}
//$boxes = 1;
//switch ($count) {
//case ($count 14):
//$boxes = 3;
//break;
//case ($count 7 $count = 14):
//$boxes = 2;
//break;
//case ($count = 7):
//default :
//$boxes = 1;
//break;
//}
Does anyone know the answer why using the Switch it always execute the
first
case ?
As has been pointed out you need switch(true).
That's a strange way of writing a switch, IMO. You should be using the if
version.
--
Cheers -- Tim
Maybe I'm way out of touch, but when I look at php.net for the syntax of the
switch statement I see:
switch($var){
case (value):
(do something)
case (other value):
(do something else)
}
IN your example, you are using a switch syntax that is nothing like that. I
think that your case statements are not actually evaluating the value of
$count, but are themselves evaluating to a true value that has nothing to do
with $count.
That `switch` is evaluating to true each case. It's an alternative of using
if-elseif structure.
iñ
Here's the manual reference:
http://us.php.net/manual/en/control-structures.switch.php
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Re: [PHP] Re: Switch - Case Statement Questions
On Fri, Nov 16, 2012 at 12:41 PM, Sebastian Krebs krebs@gmail.com wrote:
Beside this it can be rewritten as
switch ((int) (($count-1) / 7) {
case 0: // 1-7
case 1: // 8 - 14
default: // above 15
}
Nice code refactoring :) Just a tad obscure for someone coming along
later, perhaps.
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