New Julia user here :)
Following the scipy/julia tutorial by D. Sanders and playing around with
Macros
http://nbviewer.ipython.org/github/dpsanders/scipy_2014_julia/blob/master/Metaprogramming.ipynb
He has in there an example of macros. I was playing around with that and I
ran into a case where I don't understand why the expanded code ends up
introducing what seems to be a local variable. And this depends solely on
whether `expr2` contains `i += 1` or `i = i + 1`.
Can someone take the time to explain why i one case the macro expansion
introduces a local variable? And how would one get around that in this case?
Thanks,
-z
In [111]:
macro until(expr1, expr2)
quote
#:(
while !($expr1) # code interpolation
$expr2
end
#)
end
end
In [122]:
expr1 =
quote
i = 0
@until i==10 begin
print(i)
i += 1
end
end;
expr2 =
quote
i = 0
@until i==10 begin
print(i)
i = i + 1
end
end;
In [123]:
eval(expr1)
0123456789
In [124]:
eval(expr2)
i not defined
while loading In[124], in expression starting on line 1
in anonymous at In[122]:4
In [125]:
macroexpand(expr1)
Out[125]:
quote # In[122], line 3:
i = 0 # line 4:
begin # In[111], line 4:
while !(i == 10) # line 5:
begin # In[122], line 5:
print(i) # line 6:
i += 1
end
end
end
end
In [126]:
macroexpand(expr2)
Out[126]:
quote # In[122], line 11:
i = 0 # line 12:
begin # In[111], line 4:
while !(#3677#i == 10) # line 5:
begin # In[122], line 13:
print(#3677#i) # line 14:
#3677#i = #3677#i + 1
end
end
end
end
