AWK/Primes/FSOE

AWK/Primes/FSOE1

FSOE1 needs a number:set mapping and expressing this in AWK would blow up the code too much. (Or shorter: Maybe later.)

AWK/Primes/FSOE3

<lang awk>BEGIN {

   n=2
   while( n<100 ) {

if( n in L ) { p=L[n] del L[n] } else { p=n printf n " " } npp=n+p while( npp in L ) npp=npp+p L[npp]=p n++

   }
   print

}</lang>

Output:

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

BASH/Self Modyfying Code

$ . Thing-1033909978
$ type Thing 
Thing is a function
Thing () 
{ 
    local get='shift;local __=$1;shift;echo ${!__}' set='shift;__=$1;shift;local $__="$*";eval "$FUNCNAME () { local $(local | tr "\n" " "); $(type $FUNCNAME | tail +5)"' version=1033909978;
    eval ${!1}
}
$ Thing get version
1033909978
$ date -d@$(Thing get version) # ;-)
Sun Oct  6 13:12:58 UTC 2002
$ ##
$ ## add a new property 'show'
$ ##
$ Thing set show local
$ ##
$ ## try it
$ ##
$ Thing show
get='shift;local __=$1;shift;echo ${!__}'
set='shift;__=$1;shift;local $__="$*";eval "$FUNCNAME () { local $(local | tr "\n" " "); $(type $FUNCNAME | tail +5)"'
show=local
version=1033909978

Dc/Questions/DROP

TODO Drop top of stack without side effects

# assume there is a value in x[1337], e.g. "gold"
[gold] 1337 :x

# "trash" on the stack:
[trash]

# push x[1337] to x-stack
1337;x Sx
# deposit TOS in x[1337]
1337:
# top of x-stack to x[1337]
Lx 1337:

1337 ;x

[Stack: ]PAP f

Output:

Stack: 
gold

Sigh!

Is there really no simpler way to drop the top of stack that works for strings and numbers and in all versions of Dc?

Python/Primes/FSOE

Works with: Python version 2.x

This is a sequentialised variant of the well known sieve method (ab)using a dictionary as sparse array.

Alternatively you can describe it as finding the wheels and moving them on a tape. The only knowledge is to start looking 2 instead of starting with 1, but the original sieve does skip 1 too. 2 is not hard coded to be prime. The algorithm detects it as 1st prime and then puts the 2-wheel on the tape.

Python/Primes/FSOE1

Variant: A tape position can hold multiple wheels.

<lang python>L = {} n = 2

while 1:

       if n in L:
               P = L[n]
               del L[n] # optional - saves some memory.
       else:
               print n
               P = [n]

       for p in P:
               npp = n+p
               if npp in L:
                       L[npp].add(p)
               else:
                       L[npp] = set([p])

       n += 1</lang>

Output:

...the program has to be terminated by the user e.g. by typing ctrl-c.

Python/Primes/FSOE3

Works with: Python version 2.x

Variant: A tape position can hold one wheel.

<lang python>L = {} n = 2

while 1:

       if n in L:
               P = L[n]
               del L[n] # optional - saves some memory.
       else:
               P = n
               print n

       m = n+P
       while m in L:
               m += P
       L[m] = P

       n += 1</lang>

Output:

...the program has to be terminated by the user e.g. by typing ctrl-c.

My Favorite Languages
Language	Proficiency
AWK	---
B	---
BASH	---
C	---
Dc	---
Spin	---