Valiya, remember when you told me that all that [I] have to do is show [you] an example of a computer which took on new functions by adding bits?

So I got bored at work and wrote a little program. This program (let's call it program A) takes a different program (program B) and alters it randomly by replace 1 letter with a random letter. It then tries to run program B, and spits out interesting results. I ran it 2000 times (that is it started with the original code and mutated it once, then tried to run it, rinse repeat 2000 times).

The unmodified program B is:
def f(x,y):
print x+y
f(3,7)
Or simply, print the sum of 3 and 7.

After 'mutation':

About 90% of the time, program B crashes (which program A is protected against), so nothing is returned.

About 5% of the time, program B runs, but fails to print anything.

About 2% of the time program B runs as expected. Often times this is because a character was inserted that does nothing, like an extra space in many locations won't produce a noticeable difference in the output of function B.

About 2% of the time, one of the numbers being input in to Program B got altered (like maybe the 3 got changed to an 8).

About 1% of the time, program B runs but outputs something very unexpected. I expected to see certain mutations, and I actually saw very few of those. But I did see several very weird one. Below is a list of the ones I thought were interesting. It displays the new mutated version of the function, the output it gave, the mutation number when this occurred, and my description of the mutation.

--------------------
def f(x,y):
print x-y
f(3,7)
output = -4
mutation number: 59
Notes: Turned the addition function into a subtraction function. This is one of the few I actually anticipated.
--------------------
def f(x,y):
print -+y
f(3,7)
output = -7
mutation number: 252
Notes: This one returns the negative of y. Similar mutation in 1923.
--------------------
def f(x,y):
print 8+y
f(3,7)
output = 15
mutation number: 315
Notes: This one changed to a function that just returns y + 8, similar mutation occurred in 382, 384, 491, 11, 15, 1004, 1161, 1283, 1328, 1502, 1538, 1583, 1591, 1698, 1938.
--------------------
def z(x,y):
print x+y
f(3,7)
output = False
mutation number: 828
Note: This one renamed the function to z (instead of f), so when it tried to call it, it used the wrong name which returns the output: False
--------------------
def f(x,y):
print x%y
f(3,7)
output = 3
mutation number: 936
Notes: This mutation changes the function from calculating the sum of the 1st and 2nd number, to calculating their modulo.
--------------------
def f(x,y):
print x