amazing for loop

[nyso]

Hi all,

I tried this :
for( $i = 'M' ; $i <= 'Y' ; $i++) {
$alpha_2 .= $i."&nbsp;&nbsp;&nbsp;" ;
}
I get :
M N O P Q R S T U V W X Y
=> no problem

BUT !
Try this :
for( $i = 'M' ; $i <= 'X' ; $i++) {
$alpha_2 .= $i."&nbsp;&nbsp;&nbsp;" ;
}
I get :
M N O P Q R S T U V W X Y Z AA AB AC AD
AE AF AG AH AI AJ AK AL AM AN AO AP AQ AR AS
AT AU AV AW AX AY AZ BA BB BC BD BE BF BG BH
BI BJ BK BL BM BN BO BP BQ BR BS BT BU BV BW
BX BY BZ CA CB CC CD CE CF CG CH CI CJ CK CL
CM CN CO CP CQ CR CS CT CU CV CW CX CY CZ DA
DB DC DD DE DF DG DH DI DJ DK DL DM DN DO DP
DQ DR DS DT DU DV DW DX DY DZ EA EB EC ED EE
EF EG EH EI EJ EK EL EM EN EO EP EQ ER ES ET
EU EV EW EX EY EZ FA FB FC FD FE FF FG FH FI
FJ FK FL FM FN FO FP FQ FR FS FT FU FV FW FX
FY FZ GA GB GC GD GE GF GG GH GI GJ GK GL GM
GN GO GP GQ GR GS GT GU GV GW GX GY GZ HA HB
HC HD HE HF HG HH HI HJ HK HL HM HN HO HP HQ
HR HS HT HU HV HW HX HY HZ IA IB IC ID IE IF
IG IH II IJ IK IL IM IN IO IP IQ IR IS IT IU
IV IW IX IY IZ JA JB JC JD JE JF JG JH JI JJ
JK JL JM JN JO JP JQ JR JS JT JU JV JW JX JY
JZ KA KB KC KD KE KF KG KH KI KJ KK KL KM KN
KO KP KQ KR KS KT KU KV KW KX KY KZ LA LB LC
LD LE LF LG LH LI LJ LK LL LM LN LO LP LQ LR
LS LT LU LV LW LX LY LZ MA MB MC MD ME MF MG
MH MI MJ MK ML MM MN MO MP MQ MR MS MT MU MV
MW MX MY MZ NA NB NC ND NE NF NG NH NI NJ NK
NL NM NN NO NP NQ NR NS NT NU NV NW NX NY NZ
OA OB OC OD OE OF OG OH OI OJ OK OL OM ON OO
OP OQ OR OS OT OU OV OW OX OY OZ PA PB PC PD
PE PF PG PH PI PJ PK PL PM PN PO PP PQ PR PS
PT PU PV PW PX PY PZ QA QB QC QD QE QF QG QH
QI QJ QK QL QM QN QO QP QQ QR QS QT QU QV QW
QX QY QZ RA RB RC RD RE RF RG RH RI RJ RK RL
RM RN RO RP RQ RR RS RT RU RV RW RX RY RZ SA
SB SC SD SE SF SG SH SI SJ SK SL SM SN SO SP
SQ SR SS ST SU SV SW SX SY SZ TA TB TC TD TE
TF TG TH TI TJ TK TL TM TN TO TP TQ TR TS TT
TU TV TW TX TY TZ UA UB UC UD UE UF UG UH UI
UJ UK UL UM UN UO UP UQ UR US UT UU UV UW UX
UY UZ VA VB VC VD VE VF VG VH VI VJ VK VL VM
VN VO VP VQ VR VS VT VU VV VW VX VY VZ WA WB
WC WD WE WF WG WH WI WJ WK WL WM WN WO WP WQ
WR WS WT WU WV WW WX WY WZ XA XB XC XD XE XF
XG XH XI XJ XK XL XM XN XO XP XQ XR XS XT XU
XV XW XX XY XZ YA YB YC YD YE YF YG YH YI YJ
YK YL YM YN YO YP YQ YR YS YT YU YV YW YX YY
YZ
=> hum... what's the problem ?

any idea ?

thanks in advance,
--
nyso

[nyso]

> for( $i = 'M' ; $i <= 'X' ; $i++) {

> $alpha_2 .= $i."&nbsp;&nbsp;&nbsp;" ;
> }

I meant :

> for( $i = 'M' ; $i <= 'Z' ; $i++) {

sorry !
--
nyso

[Alvaro G Vicario]

*** nyso wrote/escribió (Thu, 20 Nov 2003 09:56:27 +0100):

> for( $i = 'M' ; $i <= 'Y' ; $i++) {

'X' <= 'Y' ? --> true
'Y' <= 'Y' ? --> true
'Z' <= 'Y' ? --> false --> end

'X' <= 'Z' ? --> true
'Y' <= 'Z' ? --> true
'Z' <= 'Z' ? --> true
'AA' <= 'Z' ? --> true
'AB' <= 'Z' ? --> true
....
'YY' <= 'Z' ? --> true
'YZ' <= 'Z' ? --> true
'ZA' <= 'Z' ? --> false --> end

Please note you aren't comparing numbers but strings.


--
--
-- Álvaro G. Vicario - Burgos, Spain
--

[David Mackenzie]

On Thu, 20 Nov 2003 11:48:31 +0100, Alvaro G Vicario
<alvaro_QUITAR_REMOVE@telecomputeronline.com> wrote:

>*** nyso wrote/escribió (Thu, 20 Nov 2003 09:56:27 +0100):

>> for( $i = 'M' ; $i <= 'Y' ; $i++) {

>
>'X' <= 'Y' ? --> true
>'Y' <= 'Y' ? --> true
>'Z' <= 'Y' ? --> false --> end
>
>'X' <= 'Z' ? --> true
>'Y' <= 'Z' ? --> true
>'Z' <= 'Z' ? --> true
>'AA' <= 'Z' ? --> true
>'AB' <= 'Z' ? --> true
>...
>'YY' <= 'Z' ? --> true
>'YZ' <= 'Z' ? --> true
>'ZA' <= 'Z' ? --> false --> end
>
>Please note you aren't comparing numbers but strings.

It is interesting to see that PHP considers 'Z' + 1 == 'AA', though.

--
David ( @priz.co.uk )
The Internet Prisoner Database: [url]http://www.priz.co.uk/ipdb/[/url]
The Tarbrax Chronicle: [url]http://www.tarbraxchronicle.com/[/url]

[Justin Koivisto]

David Mackenzie wrote:

> It is interesting to see that PHP considers 'Z' + 1 == 'AA', though.

Interesting yes, but I think that it is nice that PHP doesn't base
incrementing a string solely on the ASCII value. Afterall, I think that
the following is a natural progression..

A,B...
Y,Z,AA,AB...
AY,AZ,BA,BB...
ZY,ZZ,AAA...

Afterall, when incrementing a character by adding int(1) to it, you are
simply increasing the ASCII value. After "Z" (chr(90)) would be "["
(chr(91)).

Also beware that ord('AA') will return 65 since it returns the ASCII
value of the *first* character of the string.

--
Justin Koivisto - [email]spam@koivi.com[/email]
PHP POSTERS: Please use comp.lang.php for PHP related questions,
alt.php* groups are not recommended.

[David Mackenzie]

On Thu, 20 Nov 2003 15:12:51 GMT, Justin Koivisto <spam@koivi.com>
wrote:

>David Mackenzie wrote:

>> It is interesting to see that PHP considers 'Z' + 1 == 'AA', though.

>
>Interesting yes, but I think that it is nice that PHP doesn't base
>incrementing a string solely on the ASCII value. Afterall, I think that
>the following is a natural progression..
>
>A,B...
>Y,Z,AA,AB...
>AY,AZ,BA,BB...
>ZY,ZZ,AAA...

I've just noticed that it is following exactly the same algorithm as
for incrementing "numeric" strings ("8", "9", "10", "11") except using
ASCII ranges 65..90 as opposed to 48..57.

I was once writing a function to concatenate date parts together
(before I discovered the date functions). I had:

$day = 19;
$month = "March";
$year = 1928;

The result of
$date = $day." ".$month." ".$year;

was
$date == "1947 March"

It added 19 and 1928, but preserved "March".

--
David ( @priz.co.uk )
The Internet Prisoner Database: [url]http://www.priz.co.uk/ipdb/[/url]
The Tarbrax Chronicle: [url]http://www.tarbraxchronicle.com/[/url]

[Alvaro G Vicario]

*** David Mackenzie wrote/escribió (Thu, 20 Nov 2003 11:36:54 +0000):

> It is interesting to see that PHP considers 'Z' + 1 == 'AA', though.

It is curious indeed. It's documented anyway:

«PHP follows Perl's convention when dealing with arithmetic operations on
character variables and not C's. For example, in Perl 'Z'+1 turns into
'AA', while in C 'Z'+1 turns into '[' ( ord('Z') == 90, ord('[') == 91 ).
Note that character variables can be incremented but not decremented.»

[url]http://us2.php.net/manual/en/language.operators.increment.php[/url]

(Nope, I didn't know until today ;-)


--
--
-- Álvaro G. Vicario - Burgos, Spain
--

[Default User]

Alvaro G Vicario wrote:

>
> *** David Mackenzie wrote/escribió (Thu, 20 Nov 2003 11:36:54 +0000):

> > It is interesting to see that PHP considers 'Z' + 1 == 'AA', though.

>
> It is curious indeed. It's documented anyway:
>
> «PHP follows Perl's convention when dealing with arithmetic operations on
> character variables and not C's. For example, in Perl 'Z'+1 turns into
> 'AA', while in C 'Z'+1 turns into '[' ( ord('Z') == 90, ord('[') == 91 ).
> Note that character variables can be incremented but not decremented.»

Actually, C guarantees nothing of the sort. It does not require the use
of the ASCII character set at all, and in fact some implementations do
not use it. The result of 'Z'+1 is entirely implementation-specific.

The a more correct form of the statement would be something like, "while
in strict ASCII systems, such as some implementations of C, 'Z'+1 turns
into '[' . . ."



Brian Rodenborn