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Decrementing/Incrementing operatorji PHP
PrihajaNodi ::
$d = 'A8';
for ($n=0; $n<5; $n++)
echo ++$d /
Od kje pride A9 B0, B1. Kateri del nakazuje na znak B?
Ribič ::
Tole je meni malo čudno. Kaj imaš v tisti spremenljivki $d? Meni zgleda kot nek tekstovni string, ker je v narekovajih.
Če bi imel heksadecimalno valuto, potem bi zaporedje moralo iti A8, A9, AA, AB, AC, AD, AE, AF, B0, B1, itd.
Če bi imel heksadecimalno valuto, potem bi zaporedje moralo iti A8, A9, AA, AB, AC, AD, AE, AF, B0, B1, itd.
Vse ribe so mi pobegnile!
Miha 333 ::
RTFM: http://php.net/manual/en/language.opera... in http://perldoc.perl.org/perlop.html#Aut... (pravilo je isto kot pri Perl).
PHP follows Perl's convention when dealing with arithmetic operations on character variables and not C's. For example, in PHP and Perl $a = 'Z'; $a++; turns $a into 'AA', while in C a = 'Z'; a++; turns a into '[' (ASCII value of 'Z' is 90, ASCII value of '[' is 91). Note that character variables can be incremented but not decremented and even so only plain ASCII alphabets and digits (a-z, A-Z and 0-9) are supported. Incrementing/decrementing other character variables has no effect, the original string is unchanged.
PHP follows Perl's convention when dealing with arithmetic operations on character variables and not C's. For example, in PHP and Perl $a = 'Z'; $a++; turns $a into 'AA', while in C a = 'Z'; a++; turns a into '[' (ASCII value of 'Z' is 90, ASCII value of '[' is 91). Note that character variables can be incremented but not decremented and even so only plain ASCII alphabets and digits (a-z, A-Z and 0-9) are supported. Incrementing/decrementing other character variables has no effect, the original string is unchanged.
The above example will output:
== Characters ==
X
Y
Z
AA
AB
AC
== Digits ==
A9
B0
B1
B2
B3
B4
A09
A10
A11
A12
A13
A14
Incrementing or decrementing booleans has no effect.
The auto-increment operator has a little extra builtin magic to it. If you increment a variable that is numeric, or that has ever been used in a numeric context, you get a normal increment. If, however, the variable has been used in only string contexts since it was set, and has a value that is not the empty string and matches the pattern /^[a-zA-Z]*[0-9]*\z/ , the increment is done as a string, preserving each character within its range, with carry:
print ++($foo = "99"); # prints "100"
print ++($foo = "a0"); # prints "a1"
print ++($foo = "Az"); # prints "Ba"
print ++($foo = "zz"); # prints "aaa"
Zgodovina sprememb…
- spremenilo: Miha 333 ()
mojster_joni ::
Miha 333 ::
Tudi v PHPju je konsistentnost, samo moraš vedet, s čim imaš opravka in kaj hočeš.
string: $a = 'AF';
integer (v hex obliki): $a = 0x1A;
Zgoraj je govora izključno o stringih, prilepil pa sem pravilo iz navodil, kaj se z njimi dogaja, če jih povečuješ in nima veze s hexadecimalnimi števili. Vse je v navodilih.
string: $a = 'AF';
integer (v hex obliki): $a = 0x1A;
Zgoraj je govora izključno o stringih, prilepil pa sem pravilo iz navodil, kaj se z njimi dogaja, če jih povečuješ in nima veze s hexadecimalnimi števili. Vse je v navodilih.
technolog ::
String increment je feature, ki ga poznajo tudi drugi programski jeziki, npr. Ruby:
"z".next # vrne string "aa"
@Vesoljc: Pojma nimas.
"z".next # vrne string "aa"
@Vesoljc: Pojma nimas.
PrihajaNodi ::
Porabljeno kar nekaj casa kaj ima to veza s hexadecimalnimi stevili.
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Hvala
Zgodovina sprememb…
- spremenilo: PrihajaNodi ()