13 Sep
2014
13 Sep
'14
2:02 a.m.
On Fri, 12 Sep 2014, random832(a)fastmail.us wrote:
What language does the undocumented option (assuming
it is supported at
all) "bc -c" generate on FreeBSD and OSX? "Standard" bc, which
actually
pipes to dc, generates (obviously) dc when run in this way, but GNU bc
generates a completely different and as far as I know undocumented
language, which is handled by the execute function (in execute.c) but as
far as I know there is no way to make it accept it on standard input.
According to my trusty Mac:
DIFFERENCES
This version of bc was implemented from the POSIX P1003.2/D11 draft and
contains several differences and extensions relative to the draft and
traditional implementations. It is not implemented in the traditional
way using dc(1). This version is a single process which parses and
runs a byte code translation of the program. There is an "undocu-
mented" option (-c) that causes the program to output the byte code to
the standard output instead of running it. It was mainly used for
debugging the parser and preparing the math library.
My trusty FreeBSD box says the same thing. Well, they're both Gnu 1.06,
after all, and it's some sort of byte-code. I can sort see how it works;
single digit integers, unless wrapped by "Knnn:" etc..
Standard bc:
$ echo '2+2' | bc -c
2 2+ps.
q$
GNU bc:
$ echo '2+2' | bc -c
@iK2:K2:+W@r
@i
$
Oops; a "1" stands for itself, but other ints are bracketed:
davehorsmacbook:~ dave$ bc -c
@ibc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
1+1
11+W@r
@i2+2
K2:K2:+W@r
@i
Amusing that it treats "1" and "not 1" differently. Oh, and
"0" stands
for itself. One more test:
00+W@r
@i-1+1
1n1+W@r
So, that's something like "1 negate 1 add" - gasp, that's RPN!
I'd check
the sources if I had them (none for Mac, and I didn't bother with FBSD).
-- Dave