You need to call esc on the expressions to provide macro hygiene. Sorry for the brief reply, but let me know if that helps. Btw, did you mean to include output from macroexpand above? If so, it doesn't seem to have gotten included.
On Sun, Sep 14, 2014 at 9:28 PM, Zouhair Mahboubi < [email protected]> wrote: > 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 > >
