I would like to add a "%b" format for converting numbers to binary format (1's and 0's). I realize this isn't a C-ism, but it would be very useful for teaching purposes, as newcomers find 101101 a lot easier to understand than 0x2D.
Reactions?
Greg
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Greg Wilson Greg.Wilson@baltimore.com:
I would like to add a "%b" format for converting numbers to binary format (1's and 0's). I realize this isn't a C-ism, but it would be very useful for teaching purposes, as newcomers find 101101 a lot easier to understand than 0x2D.
Reactions?
+1. Didactically pretty useful, and the additional code won't boost global complexity much.
"Eric S. Raymond" wrote:
Greg Wilson Greg.Wilson@baltimore.com:
I would like to add a "%b" format for converting numbers to binary format (1's and 0's). I realize this isn't a C-ism, but it would be very useful for teaching purposes, as newcomers find 101101 a lot easier to understand than 0x2D.
Reactions?
+1. Didactically pretty useful, and the additional code won't boost global complexity much.
Good idea. The only question I have is: in which order will you print the 0s and 1s (MSB->LSB, LSB->MSB, little/big endian) ?
I am thinking of adding a bit field type to mxNumber and have the same problem there...
M.-A. Lemburg mal@lemburg.com:
I would like to add a "%b" format for converting numbers to binary format (1's and 0's). I realize this isn't a C-ism, but it would be very useful for teaching purposes, as newcomers find 101101 a lot easier to understand than 0x2D.
+1. Didactically pretty useful, and the additional code won't boost global complexity much.
Good idea. The only question I have is: in which order will you print the 0s and 1s (MSB->LSB, LSB->MSB, little/big endian) ?
I am thinking of adding a bit field type to mxNumber and have the same problem there...
For *this* context, we clearly want mathematical notation; MSB to the right and no byte-swapping. After all we'd actually be printing numerals, not dumping a bitfield.
[Greg Wilson]
I would like to add a "%b" format for converting numbers to binary format (1's and 0's).
-0, due to compound lumpiness: hex() is to %x is to __hex__ as oct() is to %o is to __oct__ as nothing is to %b is to nothing. In that respect it's unfortunate that Python has distinct nb_oct and nb_hex slots in the PyNumberMethods struct (as opposed to a single parameterized "convert to base N string" method).
[MAL]
Good idea. The only question I have is: in which order will you print the 0s and 1s (MSB->LSB, LSB->MSB, little/big endian) ?
I'm sure Greg has in mind only integers, in which case %x and %o already give the only useful <wink> answer.
Tim Peters tim.one@home.com:
-0, due to compound lumpiness: hex() is to %x is to __hex__ as oct() is to %o is to __oct__ as nothing is to %b is to nothing. In that respect it's unfortunate that Python has distinct nb_oct and nb_hex slots in the PyNumberMethods struct (as opposed to a single parameterized "convert to base N string" method).
Is the right answer to add the convert-to-base slot and deprecate the other two?
[Eric S. Raymond]
Is the right answer to add the convert-to-base slot and deprecate the other two?
That would fix "the other" lump here in Python, that e.g.
int("111", 3)
13
has no inverse. string->int is happy with any base in 2..36 inclusive, but int->string is spelled via 3 different builtins covering only 3 of those bases.
It would be more *expedient* to add "just" a __bin__/nb_bin method + a way to spell binary int literals + a %b format + a bin() builtin.
On the fifth hand, I doubt anyone would want to add new % format codes for bases {2..36} - {2, 8, 10, 16}.
So it will remain lumpy no matter what. I look forward to the PEP <wink>.
Tim Peters tim.one@home.com:
[Eric S. Raymond]
Is the right answer to add the convert-to-base slot and deprecate the other two?
That would fix "the other" lump here in Python, that e.g.
int("111", 3)
13
has no inverse. string->int is happy with any base in 2..36 inclusive, but int->string is spelled via 3 different builtins covering only 3 of those bases.
That sounds like a strong argument to me.
Tim:
On the fifth hand, I doubt anyone would want to add new % format codes for bases {2..36} - {2, 8, 10, 16}.
So, just add one general one:
%m.nb
with n being the base. If n defaults to 2, you can read the "b" as either "base" or "binary".
Literals:
0b(5)21403 general 0b11001101 binary
Conversion functions:
base(x, n) general bin(x) equivalent to base(x, 2) (for symmetry with existing hex, oct)
Type slots:
__base__(x, n)
Backwards compatibility measures:
hex(x) --> base(x, 16) oct(x) --> base(x, 8) bin(x) --> base(x, 2)
base(x, n) checks __hex__ and __oct__ slots for special cases of n=16 and n=8, falls back on __base__
There, that takes care of integers. Anyone want to do the equivalent for floats ?-)
Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | A citizen of NewZealandCorp, a | Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. | greg@cosc.canterbury.ac.nz +--------------------------------------+
Greg Ewing greg@cosc.canterbury.ac.nz:
So, just add one general one:
%m.nb
with n being the base. If n defaults to 2, you can read the "b" as either "base" or "binary".
I had a similar idea, but your version is more elegant.
[Greg Ewing]
So, just add one general one:
%m.nb
with n being the base. If n defaults to 2, you can read the "b" as either "base" or "binary".
Except .n has a different meaning already for integer conversions:
"%.5d" % 2
'00002'
"%.10o" % 377
'0000000571'
It would be inconsistent to hijack it to mean something else here.
Literals:
0b(5)21403 general
I've actually got no use for bases outside {2, 8, 10, 16), and have never heard a request for them either, so I'd be at best -0. Better to stop documenting the full truth about int() <0.9 wink>.
0b11001101 binary
+1.
Conversion functions:
base(x, n) general
-0, as above.
bin(x) equivalent to base(x, 2) (for symmetry with existing hex, oct)
+1 if binary literals are added.
Type slots:
__base__(x, n)
Given the tenor of the above, add __bin__ and call it a day.
Backwards compatibility measures:
hex(x) --> base(x, 16) oct(x) --> base(x, 8) bin(x) --> base(x, 2)
base(x, n) checks __hex__ and __oct__ slots for special cases of n=16 and n=8, falls back on __base__
There, that takes care of integers. Anyone want to do the equivalent for floats ?-)
Note that C99 introduces a hex notation for floats.
"GW" == Greg Wilson Greg.Wilson@baltimore.com writes:
GW> I would like to add a "%b" format for converting numbers to GW> binary format (1's and 0's).
For completeness, wouldn't you also want a binary integer literal so your students could write binary numbers in their code? And what about a binary() operator a la hex()?
-Barry
Barry A. Warsaw barry@digicool.com:
"GW" == Greg Wilson Greg.Wilson@baltimore.com writes:
GW> I would like to add a "%b" format for converting numbers to GW> binary format (1's and 0's).For completeness, wouldn't you also want a binary integer literal so your students could write binary numbers in their code? And what about a binary() operator a la hex()?
Barry is correct. If we're going to do this, we ought to do it right and support binary on a par with decimal, hex, and octal. I favor this.
Note that in Vyper (John Skaller's Python variant) these are legit integer literals:
0b11111111 0B11111111 0o777 0O777 0d999 0D999 0xfFf 0XFFf
Vyper's octal notation is still ugly, but whoever first thought
0777 != 777
was a "good idea" was certifiably insane <0.25 wink>.
Tim Peters tim.one@home.com:
Vyper's octal notation is still ugly, but whoever first thought
0777 != 777was a "good idea" was certifiably insane <0.25 wink>.
For anyone who doesn't know the history behind this...
The 0xxx notation was copied from PDP-11 assembler literals -- the instruction-set design of the PDP-11 was such that most of the instruction subfields fit in octal digits, so this convention made it somewhat easier to read machine-code dumps.
While I'm at it, I should note that the design of the 11 was ancestral to both the 8088 and 68000 microprocessors, and thus to essentially every new general-purpose computer designed in the last fifteen years.
[ESR]
The 0xxx notation was copied from PDP-11 assembler literals -- the instruction-set design of the PDP-11 was such that most of the instruction subfields fit in octal digits, so this convention made it somewhat easier to read machine-code dumps.
That doesn't mean they weren't certifiably insane. At Cray, we had a much more sensible convention: *all* numbers were octal (yes, it was a 64-bit box and octal didn't make any sense, but Seymour Cray got used to it from the 60-bit CDC w/ 18-bit address registers and didn't feel like changing). My first boss there loved telling the story about he was out for a drive with the family, and excitedly screamed "Hey, kids! Look! The odometer is just about to change to 40,000!". Of course it read 37,777.9 at the time, and they thought he was nuts. That's where this kind of thing always leads in the end.
to-disgrace-despair-and-eventually-ruin-ly y'rs - tim
Eric wrote:
While I'm at it, I should note that the design of the 11 was ancestral to both the 8088 and 68000 microprocessors, and thus to essentially every new general-purpose computer designed in the last fifteen years.
The key to PDP-11 and VAX was lots of registers all a like and rich addressing modes for the instructions.
The 8088 is very far from this design, its owes its design more to 4004 then the PDP-11.
However the 68000 is the closer, but not as nice to program as there are too many special cases in its instruction set for my liking.
BArry
Barry Scott barry@scottb.demon.co.uk:
Eric wrote:
While I'm at it, I should note that the design of the 11 was ancestral to both the 8088 and 68000 microprocessors, and thus to essentially every new general-purpose computer designed in the last fifteen years.
The key to PDP-11 and VAX was lots of registers all a like and rich addressing modes for the instructions.
The 8088 is very far from this design, its owes its design more to 4004 then the PDP-11.
Yes, but the 4004 was designed as a sort of lobotomized imitation of the 65xx, which was descended from the 11. Admiitedly, in the chain of transmission here were two stages of redesign so bad that the connection got really tenuous.
Eric> Yes, but the 4004 was designed as a sort of lobotomized imitation Eric> of the 65xx, which was descended from the 11.
Really? I was always under the impression the 4004 was considered the first microprocessor. The page below says that and gives a date of 1971 for it. I have no idea if the author is correct, just that what he says agrees with my memory. He does seem to have an impressive collection of old computer iron:
http://www.piercefuller.com/collect/i4004/
I haven't found a statement about the origins of the 6502, but this page suggests that commercial computers were being made from 8080's before 6502's:
http://www.speer.org/2backup/pcbs_pch.html
Ah, wait a minute... This page:
http://www.geocities.com/SiliconValley/Byte/6508/6502/english/versoes.htm
says the 6502 was descended from the 6800. I'm getting less and less convinced that the 4004 somehow descended from the 65xx family.
(Maybe we should shift this thread to the always entertaining folks at comp.arch... ;-)
Skip
Skip Montanaro skip@pobox.com:
Really? I was always under the impression the 4004 was considered the first microprocessor. The page below says that and gives a date of 1971 for it.
First sentence is widely believed, but there was an earlier micro called the Star-8 designed at Burroughs that has been almost completely forgotten. I only know about it because I worked there in 1980 with one of the people who designed it.
I think I had a brain fart and it's the Z80 that was descended from the 6502. I was going by a remark in some old lecture notes. I've got a copy of the definitive reference on history of computer architecture and will check.
Eric> Skip Montanaro skip@pobox.com: >> Really? I was always under the impression the 4004 was considered >> the first microprocessor. The page below says that and gives a date >> of 1971 for it.
Eric> First sentence is widely believed, but there was an earlier micro Eric> called the Star-8 designed at Burroughs that has been almost Eric> completely forgotten.
There was also a GE-8 (I think that was the name) developed at GE's R&D Center in the early 1970's timeframe - long before my time there. It was apparently very competitive with the other microprocessors produced about that time but never saw the light of day. I suspect that was at least due in part to the fact that GE built mainframes back then.
Skip
Eric, As others have pointed out your time line is wrong...
BArry p.s. I'm ex-DEC and old enough to have seen the introduction of the 6502 (got mine at university for $25 inc postage to the U.K.), Z80 and VAX (worked on product for V1.0 of VMS). Also for my sins argued with Gordon Bell and Dave Cutler about CPU architecture.
-----Original Message----- From: Eric S. Raymond [mailto:esr@thyrsus.com] Sent: 04 June 2001 21:11 To: Barry Scott Cc: python-dev (E-mail) Subject: Re: [Python-Dev] %b format? - 8088 like a PDP-11 I think not...
Barry Scott barry@scottb.demon.co.uk:
Eric wrote:
While I'm at it, I should note that the design of the 11 was ancestral to both the 8088 and 68000 microprocessors, and thus to essentially every new general-purpose computer designed in the last fifteen years.
The key to PDP-11 and VAX was lots of registers all a like and rich addressing modes for the instructions.
The 8088 is very far from this design, its owes its design more to 4004 then the PDP-11.
Yes, but the 4004 was designed as a sort of lobotomized imitation of the 65xx, which was descended from the 11. Admiitedly, in the chain of transmission here were two stages of redesign so bad that the connection got really tenuous. -- <a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a>
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