# Syntaxe noweb ?

#+title:
#+date:
#+author:
#+options: toc:nil

#+property: header-args:python :session
#+property: header-args:sage :session

Seen in ~org-mode~ version src_emacs-lisp{org-version}.

Using ~noweb~ syntax works OK with ~emacs-lisp~:

#+begin_example
#+name: a
#+begin_src emacs-lisp
  (setq L (append L (list i)))
#+end_src

#+name: b
#+begin_src emacs-lisp :noweb yes :exports both
  ;; Lisp version
  (setq L nil)
  (dotimes (i 5) <<a>>)
  L
#+end_src
#+end_example

This gives :

#+name: a
#+begin_src emacs-lisp
  (setq L (append L (list i)))
#+end_src

#+name: b
#+begin_src emacs-lisp :noweb yes :exports both
  ;; Lisp version
  (setq L nil)
  (dotimes (i 5) <<a>>)
  L
#+end_src

The ~noweb~ syntax also works with ~Sage~ (a symbolic maths oriented
Python derivative):

#+begin_example
#+name: Aaarghhh
#+begin_src sage
  L.append(i)
#+end_src

#+name: Berde
#+begin_src sage :noweb yes :exports both
  ## Python version
  L=[]
  for i in range(1,6):
      <<Aaarghhh>>
  L
#+end_src
#+end_example

wich gives :

#+name: Aaarghhh
#+begin_src sage
  L.append(i)
#+end_src

#+name: Berde
#+begin_src sage :noweb yes :exports both
  ## Sage version
  L=[]
  for i in range(1,6):
      <<Aaarghhh>>
  L
#+end_src

But using the same syntax in Python fails miserably:

#+begin_example
#+name: Ah
#+begin_src python
  L.append(i)
#+end_src

#+name: Beee
#+begin_src python :noweb yes :exports both
  ## Python version
  L=[]
  for i in range(1,6):
      <<Ah>>
  L
#+end_src
#+end_example

#+name: Ah
#+begin_src python
  L.append(i)
#+end_src

#+name: Beee
#+begin_src python :noweb yes :exports both
  ## Python version
  L=[]
  for i in range(1,6):
      <<Ah>>
  L
#+end_src

It *seems* that the "Ah" block is not expanded.

The code itself should be sound *if* it expanded:

#+begin_example
#+name: B0
#+begin_src python :exports both
  L=[]
  for i in range(1,6):
      L.append(i)
  L
#+end_src
#+end_example

#+name: B0
#+begin_src python :exports both
  L=[]
  for i in range(1,6):
      L.append(i)
  L
#+end_src

During the compilation of the source of this mail, the following is
printed in the ~*Python*~ buffer:

#+begin_example
>>> L.append(i)
>>> 
>>> open('/tmp/babel-OJSsxf/python-dVESY4', 'w').write(str(_))
>>> 
>>> 
>>> 'org_babel_python_eoe'
'org_babel_python_eoe'
>>> ## Python version
... L=[]
>>> for i in range(1,6):
...     <<Ah>>
  File "<stdin>", line 2
    <<Ah>>
     ^
SyntaxError: invalid syntax
>>> 
>>> L
[]
>>> 
>>> open('/tmp/babel-OJSsxf/python-9NR46u', 'w').write(str(_))
>>> 
>>> 
>>> 'org_babel_python_eoe'
'org_babel_python_eoe'
>>> L=[]
>>> for i in range(1,6):
...     L.append(i)
... 
>>> L
[1, 2, 3, 4, 5]
>>> 
>>> open('/tmp/babel-OJSsxf/python-fW5gK0', 'w').write(str(_))
>>> 
>>> 
>>> 'org_babel_python_eoe'
'org_babel_python_eoe'
>>> 
#+end_example