Code Golf: Morris Sequence

code-golflanguage-agnosticrosetta-stone

The Challenge

The shortest code by character count that will output the Morris Number Sequence. The Morris Number Sequence, also known as the Look-and-say sequence is a sequence of numbers that starts as follows:

1, 11, 21, 1211, 111221, 312211, ...

You can generate the sequence infinitely (i.e, you don't have to generate a specific number).

I/O Expectations

The program doesn't need to take any input (but bonus points for accepting input and thereby providing the option to start from any arbitrary starting point or number). At the very least your program must start from 1.

Output is at the very least expected to be the sequence:

Extra Credit

If you're going for extra credit, you would need to do something like this:

$ morris 1
1
11
21
1211
111221
312211
...

$ morris 3
3
13
1113
3113
132113
...

Best Answer

GolfScript - 41 (extra credit: 40)

1{.p`n+0:c:P;{:|P=c{c`P|:P!}if):c;}%~1}do
{~.p`n+0:c:P;{:|P=c{c`P|:P!}if):c;}%1}do

What?
The procedure for getting the next number in the sequence: Convert the current number to a string, append a newline and loop over the characters. For each digit, if the previous digit P is the same, increment the counter c. Otherwise, add c and P to what will be next number, then update these variables. The newline we append allows the last group of digits to be added to the next number.

The exact details can be obtained examining the GolfScript documentation. (Note that | is used as a variable.)

x86 machine code (37 bytes)

Hexdump:

6800B807BF8007BE8200B40EAC3C0D741338D8740A720481EF400181C7A000AB86C3EBE8C3

Run in MS-DOS with 50 line console, the input is taken from the command line.

E.g.

wave.com 1234567890qwertyuiopasdfghjklzxcvbnm

Download binary here

Update: Shaved off three bytes thanks to jrandomhacker

Code Golf: Seven Segments

Perl, 134 characters

All linebreaks may be removed.

@s=unpack"C*",~"P\xdbLI\xc3a`[\@AB\xe0t\xc8df";
$_=<>;for$s(6,3,0){print map$s[hex$&]&1<<$_+$s?$_%2?"_":"|":" ",
0..2while/./g;print$/}

Explanation

@s stores the bits for each segment. The entries are in order from 0 to F (thanks to hex()) and the bits map to segments in this order:

6 7 x
3 4 5
0 1 2

with 0 being the LSB. (Bit 6 is unused). The values are stored packed in the string bit-inverted so there are a lot more printable characters; the ~ operator flips the bits and unpack gives me numbers (perl's bitwise operators are much clumsier when it comes to strings).

With the data in hand I read the input and proceed to loop over it three times; the only difference between the three loops is the bitmask required. For each character of input three characters of output are printed. The character to be printed is

$s[ hex $& ] & (1 << ($_ + $s) )
? ($_ % 2 ? "_" : "|" )
: " "

where @s is the lookup table, $s is the shift in effect depending on the row, and $_ is whether we're printing the 1st, 2nd, or 3rd character in the row. If the right bit in the lookup table entry is false it prints a space; otherwise it prints a "|" on the sides or a "_" in the middle.