define loop statement?

[David Isaac]

I would like to be able to define a loop statement
(nevermind why) so that I can write something like

loop 10:
do_something

instead of

for i in range(10):
do_something

Possible? If so, how?

Thanks,
Alan Isaac

[Jonathan Gardner]

No, not in the way you think it is. What you can do instead is
something like this:

def do_something(i) :
... do_something ...

def loop(n, func):
for i in range(n): func(i)

loop(10, do_something)

[Georg Brandl]

David Isaac wrote:

I would like to be able to define a loop statement
(nevermind why) so that I can write something like

loop 10:
do_something

instead of

for i in range(10):
do_something

Possible? If so, how?

It's not possible to create a new statement, with suite
and indentation rules without hacking the interpreter or
resorting to alternative bytecode compilers such as "pyc".

Creating a _function_ named "loop" is easy as Jonathan's
answer shows.

Georg

[Rene Pijlman]

David Isaac:

I would like to be able to define a loop statement
(nevermind why) so that I can write something like

loop 10:
do_something

instead of

for i in range(10):
do_something

Possible? If so, how?

Yes. By implementing a compiler or an interpreter for your programming
language. Or a preprocessor that converts your language to Python, or some
other suitable intermediate language. Or a programmer, that converts your
pseudocode and some coffee to the desired algorithm :-)

--
René Pijlman

[bearophileHUGS]

David Isaac:

I would like to be able to define a loop statement
(nevermind why) so that I can write something like

loop 10:
do_something

instead of

for i in range(10):
do_something

Possible? If so, how?

It seems that you are looking for macros; maybe Logix "language"
(www.livelogix.net/logix) or Boo (boo.codehaus.o rg) can solve your
problem.
Otherwise you can do it with very different languages like Lisp or
Scheme (with a different syntax) and maybe Dylan too.

If you tell us your purpose, maybe we can suggest you a
better/different solution.

Bye,
bearophile

[Xavier Morel]

Rene Pijlman wrote:

David Isaac:

I would like to be able to define a loop statement
(nevermind why) so that I can write something like

loop 10:
do_something

instead of

for i in range(10):
do_something

Possible? If so, how?

Yes. By implementing a compiler or an interpreter for your programming
language. Or a preprocessor that converts your language to Python, or some
other suitable intermediate language. Or a programmer, that converts your
pseudocode and some coffee to the desired algorithm :-)

Or by hacking through the Python source and creating his own "somehow
pythonish but absolutely not python" language

[Xavier Morel]

Rene Pijlman wrote:

David Isaac:

I would like to be able to define a loop statement
(nevermind why) so that I can write something like

loop 10:
do_something

instead of

for i in range(10):
do_something

Possible? If so, how?

Yes. By implementing a compiler or an interpreter for your programming
language. Or a preprocessor that converts your language to Python, or some
other suitable intermediate language. Or a programmer, that converts your
pseudocode and some coffee to the desired algorithm :-)

Or by hacking through the Python source and creating his own "somehow
pythonish but absolutely not python" language

[Jeffrey Schwab]

David Isaac wrote:

I would like to be able to define a loop statement
(nevermind why) so that I can write something like

loop 10:
do_something

instead of

for i in range(10):
do_something

Possible? If so, how?

Ruby and Smalltalk are both good at this kind of thing, since they have
syntactic support for associating a block with each method call. In
Python, I think you just have to do a little more setup. How about
something like this?

class Loop:
def __init__(self, n):
self.n = n
def __call__(self):
self.n = self.n - 1
return self.n != 0
if __name__ == '__main__':
loop = Loop(10)
while loop:
print "OK"

[Georg Brandl]

Jeffrey Schwab wrote:

class Loop:
def __init__(self, n):
self.n = n
def __call__(self):
self.n = self.n - 1
return self.n != 0
if __name__ == '__main__':
loop = Loop(10)
while loop:
print "OK"

Seems you forgot "()" after "while loop" above.

Georg

[Jeffrey Schwab]

Jeffrey Schwab wrote:

class Loop:
def __init__(self, n):
self.n = n
def __call__(self):
self.n = self.n - 1
return self.n != 0
if __name__ == '__main__':
loop = Loop(10)
while loop:
Whoops. Should be "while loop()".
print "OK"