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=DC/Questions/DROP=
TODO Drop top of stack without side effects
<pre>
# 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
</pre>
{{out}}
<pre>
Stack:
gold
</pre>
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|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.
<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>
{{out}}
<pre>
2
3
5
7
11
13
17
19
23
29
</pre>
...the program has to be terminated by the user e.g. by typing ctrl-c.
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