Re: ' or no?

oct accepts the octal, hex or binary representation of a number, a string, as argument. That string is converted to a number. Only pass strings to oct. It doesn't make sense to pass numbers to oct.

oct(0xFF) is the same thing as oct(255). oct requires a string, so 255 is converted to a string, and oct("255") == 173.
oct(0b10000) is the same thing as oct(16). oct requires a string, so 16 is converted to a string, and oct("16") == 14.
When use strict; is not used, barewords that aren't function calls are treated as string literals. ff is therefore the same thing as 'ff'.

#!perl -l
print 0255;             # 173
print oct('255');       # 173
print oct(255);         # 173
print oct(0xFF);        # 173
print oct(0b11111111);  # 173
print oct(250+5);       # 173

print 255;              # 255
print 0xFF;             # 255
print 0b11111111;       # 255
print 250+5;            # 255

print 016;              #  14
print oct('16');        #  14
print oct(16);          #  14
print oct(0x10);        #  14
print oct(0b00010000);  #  14
print oct(10+6);        #  14

print 16;               #  16
print 0x10;             #  16
print 0b00010000;       #  16
print 10+6;             #  16
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Comment on Re: ' or no? Select or Download Code

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Re^2: ' or no? by Sartak (Hermit) on Dec 28, 2006 at 03:40 UTC
In other words, a bare 0xFF is converted to 255 by the parser before oct ever sees it. (I'm not sure if this conversion actually happens, but intuitively that's what's happening)	[reply]
Re^3: ' or no? by ikegami (Patriarch) on Dec 28, 2006 at 04:06 UTC
I'm not sure if this conversion actually happens Yes, it does. A more precise wording of what happens is: "The Perl literal `0xFF` is converted to the numerical value 255 by the parser before `oct` ever sees it." `oct`, requiring a string, converts the numerical value 255 to the string value 255. Doing it's job, `oct` then converts the string value `255` to the numerical value 173.	[reply] [d/l] [select]
Re^2: ' or no? by xiaoyafeng (Deacon) on Dec 28, 2006 at 03:48 UTC
But that means oct convert a string to a number?strange logic.and according to perl theroy,number and string are one type "scalar". Anyway,thanks for your answer!	[reply]
Re^3: ' or no? by ikegami (Patriarch) on Dec 28, 2006 at 03:56 UTC
Strings, numbers and many other things can be placed in a scalar. Not all scalars are numbers. Not all scalars are strings. Perl will implicitely convert back and forth as needed, possibly resulting in warnings. `print 2+3; # Number converted to string. print 'a'.3; # N->S print '2'+3; # S->N, N->S print 'z'+3; # S->N (warn), N->S print 3+undef; # U->N (warn), N->S print ''.undef; # U->S (warn) print \$a; # R->S print \$a+0; # R->N->S` [download]	[reply] [d/l]
Re^3: ' or no? by ysth (Canon) on Dec 28, 2006 at 04:12 UTC
Yes, but if you say `$scalar = 0123` (using an octal constant) the number assigned is 83, and the string value of $scalar is also "83". All perl does for you is decimal to string conversion, so there's the oct() function to convert other (string!) representations of numbers into numbers.	[reply] [d/l]
Re^4: ' or no? by xiaoyafeng (Deacon) on Dec 28, 2006 at 05:02 UTC
I see. perl stored all numbers in decimal background. right? In other word, oct and hex is needless. We could use print to replace them. maybe it's TIMTOWTDI. :)	[reply]
Re^5: ' or no? by BrowserUk (Patriarch) on Dec 28, 2006 at 05:14 UTC
Re^5: ' or no? by xiaoyafeng (Deacon) on Dec 28, 2006 at 11:33 UTC
Re^6: ' or no? by ikegami (Patriarch) on Dec 28, 2006 at 18:07 UTC
Re^5: ' or no? by ysth (Canon) on Dec 28, 2006 at 05:39 UTC
Re^5: ' or no? by ikegami (Patriarch) on Dec 28, 2006 at 06:17 UTC
Re^3: ' or no? by swampyankee (Parson) on Dec 28, 2006 at 17:21 UTC
Actually, it's not "strange logic," after all "numbers" and "characters" are just human-readable strings representing the underlying bit representations; every time you type `$x = 1234;`, the tokenizer converts it to the underlying binary representation. The tokenizer also converts `$y&nbps;= '1234';` to a binary form. oct and hex merely make the string to number conversion explicit, in the same way you would use `sprintf\|sscanf` in C or `ENCODE\|DECODE` in old (pre-Fortran 77) dialects of Fortran (now, you would use `write\|read`). Perl automatically "stringifies" and "numerifies" based on context; print needs strings as inputs, so Perl automatically converts numbers to strings. sin needs a numerical argument, so Perl will convert a string to its numerical representation. emc At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation. —Igor Sikorsky, reported in AOPA Pilot magazine February 2003.	[reply]