Finding variables in code

Question

Given some code in your language as a string, find and display all the variable names.

Examples in pseudocode:

a=2
b=3
for(i, 0->9) do b=b-10
if a=b then write "a equals b"

Returns: a b i

abcdefgh=20000000000000
bcdifhgs="hello"
if abcdefgh=bcdifhgs then da44="hax"
if abcdefgh*2=da44 then write da44

Returns: abcdefgh bcdifhgs da44

2=3
3=5
5=7
if 2=7 then exit

Returns:

a=2
while True do b=3

Returns: a b

Shortest code wins.

For stack-based languages, display the highest height of the stack.
For memory cell based languages, display all the memory cells that have been changed.

Answer 1

Python 3, 73 66 86

Now follows the updated test cases:

import sys
print(*set(compile(sys.argv[1],'','exec').co_names)-set(dir(__builtins__)))

Note that this also prints the names of non-builtin objects and methods / attributes of objects (e.g. if you use sys.argv in the input code it'll print sys and argv). Still, it does technically fit the test cases.

Assuming we're allowed to simply run the code, it can be done in 66 characters. Note that this fails the while True test case and, unlike the above solution, does not print things like sys and argv:

import sys
print(*(lambda:(exec(sys.argv[1]),set(locals())))()[1])

Answer 2

Haskell, 2

[]

Only if you take the word "variable" literally.

Answer 3

Ruby

Kind of cheating, I guess... If code contains Ruby code, then:

pre = global_variables
eval code
(global_variables - pre + local_variables + self.instance_variables - [:code, :pre]).each do |x|
  puts x.to_s
end

Example: code = "a = 3; @b = 5; $c = 6, @@d = 10"

Output:

$c
@b

Works only with global and instance vars so far.

zsh

set > /tmp/set.1
eval $code
set > /tmp/set.2
diff -a /tmp/set.1 /tmp/set.2 | grep -vE "HISTCMD|LINENO|RANDOM|SECONDS|pipestatus" | grep -E ">[^=]+"

Example:

$code = 'zzz=3; xxx="hello"'

Output

> xxx=hello
> zzz=3

Clojure, 53

(pr(map #(last %)(re-seq #"\( *def +([a-z-])+"code))

Example:

user=> (def code "(def a 1) (     def    b     ( +  3 5 )))")
#'user/code
user=> (pr(map #(last %)(re-seq #"\( *def +([a-z-]+)"code)))
("a" "b")nil
user=>

Answer 4

Python 104

import sys,re,keyword
print(set(re.findall(r"\b\w+\b",sys.argv[1]))-set(keyword.kwlist+dir(__builtins__)))

Answer 5

HQ9+ (or H9+), 0

Is cheating allowed? In this case, the solution is a program of zero length, because the language has no variables, and has no memory cells, stack or any other form of storage. So it outputs nothing.

_{First I wanted to write Brainf*ck, but then I realized the "memory cell" rule.}

Answer 6

Python, 111

I am pretty new to code golf.. tips are appreciated, but here is an alternative approach

import ast as a
s=set()
v=a.NodeVisitor
v.visit_Name=lambda t,n:s.add(n.id)
v().visit(a.parse(input()))
print s

Answer 7

MATLAB, 12

eval('<PROGRAM STRING HERE>');who