Basic switch statement
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From: Nathan Rixham on 13 Apr 2010 16:57 Robert Cummings wrote: > steve_r wrote: >> I'm new to programming, drive a truck in the day, now taking night >> courses >> to get a better job for my family. Please bear with me if this is a dumb >> question, I don't have much experience. >> >> I'm taking a night class in HTML and PHP and can't figure out a >> problem and >> can't find the answer in the book for the course ("Beginning PHP5" by >> Wrox >> Press), on the switch manual page on php.net, or in any postings to this >> mailing list. >> >> I'm trying to pass a value to a simple integer to a function, and then >> use >> that value in a switch statement. The problem I'm having is that >> regardless >> of the value of 'val', the first case statement always executes. Even >> if I >> put '$val = 0' right before the case statement, the first case statement >> executes. The syntax looks correct based on the php.net man page for >> switch >> and from the user examples. It also matches the example in the book. >> >> function check_it2($val) { >> echo gettype($val); >> switch($val) { >> case($val > 0 ): >> echo "Switch greater than 0"; >> $diff_obj = 1; >> break; >> case($val < 0 ): >> echo "Less than 0"; >> $diff_obj = -1; >> break; >> default: >> echo "Equal to 0"; >> $diff_obj = 0; >> } >> print("Here's \$diff_obj2 in the function: " . $diff_obj); >> return $diff_obj; >> } > > You're a tad confused :) > > Q: What is the result of $val > 0? > A: false. > > Q: What is the value of $val? > A: 0 > > Q: Is 0 equivalent to false? > A: Yes! > > Use an if statement for this kind of logic. This is a fantastic example of false logic and an easy pitfall. in fact this would make a great interview question! to expand a little on the various scenarios (just for clarity, Rob is right) $val = 1; 1 > 0 equates to TRUE is 1 equivalent to TRUE : YES $val = 0; 0 > 0 equates to FALSE is 0 equivalent to FALSE : YES $val = -1; -1 > 0 equates to FALSE is -1 equivalent to FALSE: YES so no matter what value you set $val to; it's always true. lovely Regards!
From: Robert Cummings on 13 Apr 2010 17:02 Nathan Rixham wrote: > Robert Cummings wrote: >> steve_r wrote: >>> I'm new to programming, drive a truck in the day, now taking night >>> courses >>> to get a better job for my family. Please bear with me if this is a dumb >>> question, I don't have much experience. >>> >>> I'm taking a night class in HTML and PHP and can't figure out a >>> problem and >>> can't find the answer in the book for the course ("Beginning PHP5" by >>> Wrox >>> Press), on the switch manual page on php.net, or in any postings to this >>> mailing list. >>> >>> I'm trying to pass a value to a simple integer to a function, and then >>> use >>> that value in a switch statement. The problem I'm having is that >>> regardless >>> of the value of 'val', the first case statement always executes. Even >>> if I >>> put '$val = 0' right before the case statement, the first case statement >>> executes. The syntax looks correct based on the php.net man page for >>> switch >>> and from the user examples. It also matches the example in the book. >>> >>> function check_it2($val) { >>> echo gettype($val); >>> switch($val) { >>> case($val > 0 ): >>> echo "Switch greater than 0"; >>> $diff_obj = 1; >>> break; >>> case($val < 0 ): >>> echo "Less than 0"; >>> $diff_obj = -1; >>> break; >>> default: >>> echo "Equal to 0"; >>> $diff_obj = 0; >>> } >>> print("Here's \$diff_obj2 in the function: " . $diff_obj); >>> return $diff_obj; >>> } >> You're a tad confused :) >> >> Q: What is the result of $val > 0? >> A: false. >> >> Q: What is the value of $val? >> A: 0 >> >> Q: Is 0 equivalent to false? >> A: Yes! >> >> Use an if statement for this kind of logic. > > This is a fantastic example of false logic and an easy pitfall. > > in fact this would make a great interview question! > > to expand a little on the various scenarios (just for clarity, Rob is right) > > $val = 1; > 1 > 0 equates to TRUE > is 1 equivalent to TRUE : YES > > $val = 0; > 0 > 0 equates to FALSE > is 0 equivalent to FALSE : YES > > $val = -1; > -1 > 0 equates to FALSE > is -1 equivalent to FALSE: YES > > so no matter what value you set $val to; it's always true. Fail on that last one. -1 is not equivalent to FALSE :B Cheers, Rob. -- http://www.interjinn.com Application and Templating Framework for PHP
From: Nathan Rixham on 13 Apr 2010 17:04 Robert Cummings wrote: > Nathan Rixham wrote: >> Robert Cummings wrote: >>> steve_r wrote: >>>> I'm new to programming, drive a truck in the day, now taking night >>>> courses >>>> to get a better job for my family. Please bear with me if this is a >>>> dumb >>>> question, I don't have much experience. >>>> >>>> I'm taking a night class in HTML and PHP and can't figure out a >>>> problem and >>>> can't find the answer in the book for the course ("Beginning PHP5" by >>>> Wrox >>>> Press), on the switch manual page on php.net, or in any postings to >>>> this >>>> mailing list. >>>> >>>> I'm trying to pass a value to a simple integer to a function, and then >>>> use >>>> that value in a switch statement. The problem I'm having is that >>>> regardless >>>> of the value of 'val', the first case statement always executes. Even >>>> if I >>>> put '$val = 0' right before the case statement, the first case >>>> statement >>>> executes. The syntax looks correct based on the php.net man page for >>>> switch >>>> and from the user examples. It also matches the example in the book. >>>> >>>> function check_it2($val) { >>>> echo gettype($val); >>>> switch($val) { >>>> case($val > 0 ): >>>> echo "Switch greater than 0"; >>>> $diff_obj = 1; >>>> break; >>>> case($val < 0 ): >>>> echo "Less than 0"; >>>> $diff_obj = -1; >>>> break; >>>> default: >>>> echo "Equal to 0"; >>>> $diff_obj = 0; >>>> } >>>> print("Here's \$diff_obj2 in the function: " . $diff_obj); >>>> return $diff_obj; >>>> } >>> You're a tad confused :) >>> >>> Q: What is the result of $val > 0? >>> A: false. >>> >>> Q: What is the value of $val? >>> A: 0 >>> >>> Q: Is 0 equivalent to false? >>> A: Yes! >>> >>> Use an if statement for this kind of logic. >> >> This is a fantastic example of false logic and an easy pitfall. >> >> in fact this would make a great interview question! >> >> to expand a little on the various scenarios (just for clarity, Rob is >> right) >> >> $val = 1; >> 1 > 0 equates to TRUE >> is 1 equivalent to TRUE : YES >> >> $val = 0; >> 0 > 0 equates to FALSE >> is 0 equivalent to FALSE : YES >> >> $val = -1; >> -1 > 0 equates to FALSE >> is -1 equivalent to FALSE: YES >> >> so no matter what value you set $val to; it's always true. > > Fail on that last one. -1 is not equivalent to FALSE :B > well that's one job I'm not getting :p cheers for the picking that one up Rob
From: Robert Cummings on 13 Apr 2010 17:06 Nathan Rixham wrote: > Robert Cummings wrote: >> Nathan Rixham wrote: >>> Robert Cummings wrote: >>>> steve_r wrote: >>>>> I'm new to programming, drive a truck in the day, now taking night >>>>> courses >>>>> to get a better job for my family. Please bear with me if this is a >>>>> dumb >>>>> question, I don't have much experience. >>>>> >>>>> I'm taking a night class in HTML and PHP and can't figure out a >>>>> problem and >>>>> can't find the answer in the book for the course ("Beginning PHP5" by >>>>> Wrox >>>>> Press), on the switch manual page on php.net, or in any postings to >>>>> this >>>>> mailing list. >>>>> >>>>> I'm trying to pass a value to a simple integer to a function, and then >>>>> use >>>>> that value in a switch statement. The problem I'm having is that >>>>> regardless >>>>> of the value of 'val', the first case statement always executes. Even >>>>> if I >>>>> put '$val = 0' right before the case statement, the first case >>>>> statement >>>>> executes. The syntax looks correct based on the php.net man page for >>>>> switch >>>>> and from the user examples. It also matches the example in the book. >>>>> >>>>> function check_it2($val) { >>>>> echo gettype($val); >>>>> switch($val) { >>>>> case($val > 0 ): >>>>> echo "Switch greater than 0"; >>>>> $diff_obj = 1; >>>>> break; >>>>> case($val < 0 ): >>>>> echo "Less than 0"; >>>>> $diff_obj = -1; >>>>> break; >>>>> default: >>>>> echo "Equal to 0"; >>>>> $diff_obj = 0; >>>>> } >>>>> print("Here's \$diff_obj2 in the function: " . $diff_obj); >>>>> return $diff_obj; >>>>> } >>>> You're a tad confused :) >>>> >>>> Q: What is the result of $val > 0? >>>> A: false. >>>> >>>> Q: What is the value of $val? >>>> A: 0 >>>> >>>> Q: Is 0 equivalent to false? >>>> A: Yes! >>>> >>>> Use an if statement for this kind of logic. >>> This is a fantastic example of false logic and an easy pitfall. >>> >>> in fact this would make a great interview question! >>> >>> to expand a little on the various scenarios (just for clarity, Rob is >>> right) >>> >>> $val = 1; >>> 1 > 0 equates to TRUE >>> is 1 equivalent to TRUE : YES >>> >>> $val = 0; >>> 0 > 0 equates to FALSE >>> is 0 equivalent to FALSE : YES >>> >>> $val = -1; >>> -1 > 0 equates to FALSE >>> is -1 equivalent to FALSE: YES >>> >>> so no matter what value you set $val to; it's always true. >> Fail on that last one. -1 is not equivalent to FALSE :B >> > > well that's one job I'm not getting :p Well you DID get 66.7%. I've met "coders" that would stare at the answer and still not understand :D Cheers, Rob. -- http://www.interjinn.com Application and Templating Framework for PHP
From: Nathan Rixham on 13 Apr 2010 17:13
Robert Cummings wrote: > Nathan Rixham wrote: >> Robert Cummings wrote: >>> Nathan Rixham wrote: >>>> Robert Cummings wrote: >>>>> steve_r wrote: >>>>>> I'm new to programming >>>>>> >>>>>> function check_it2($val) { >>>>>> echo gettype($val); >>>>>> switch($val) { >>>>>> case($val > 0 ): >>>>>> echo "Switch greater than 0"; >>>>>> >>>>> You're a tad confused :) >>>>> >>>>> Q: What is the result of $val > 0? >>>>> A: false. >>>>> >>>>> Q: What is the value of $val? >>>>> A: 0 >>>>> >>>>> Q: Is 0 equivalent to false? >>>>> A: Yes! >>>>> >>>>> Use an if statement for this kind of logic. >>>> This is a fantastic example of false logic and an easy pitfall. >>>> >>>> in fact this would make a great interview question! >>>> >>>> to expand a little on the various scenarios (just for clarity, Rob is >>>> right) >>>> >>>> $val = 1; >>>> 1 > 0 equates to TRUE >>>> is 1 equivalent to TRUE : YES >>>> >>>> $val = 0; >>>> 0 > 0 equates to FALSE >>>> is 0 equivalent to FALSE : YES >>>> >>>> $val = -1; >>>> -1 > 0 equates to FALSE >>>> is -1 equivalent to FALSE: YES >>>> >>>> so no matter what value you set $val to; it's always true. >>> Fail on that last one. -1 is not equivalent to FALSE :B >>> >> >> well that's one job I'm not getting :p > > Well you DID get 66.7%. I've met "coders" that would stare at the answer > and still not understand :D the travesty is that I spent most of yesterday on trains brushing up on / studying formal logic! |