Pass same parameter in Recursive function

[Davy]

Hi all,

Sometimes I need to pass same parameter in recursive function. From my
point of view, the style is redundant, and I don't what to use some
global style like self.A, self.B, Is there any other choice?

For example,

def func(self, x, y, A, B, C):
#x, y change in recursive call
#A, B, C change in the first layer function call, but did not change
in recursive call
if (...):
func(x, y, A, B, C)
else(...):
func(x, y, A, B, C)

Best regards,
Davy

 

[Chris Rebert]

Assuming the function is tail-recursive or the "unchanging" arguments
are immutable, just use a closure:

def func(self, x, y, A, B, C):
def _func(x,y):
return _func(g(A,B,C,x), h(A,B,C,y)) #recurse
return _func(x, y)

I'm unsure as to the performance impact of this though.

- Chris

 

[Davy]

Assuming the function is tail-recursive or the "unchanging" arguments
are immutable, just use a closure:

[SNIP]
Hi Chris,

Thank you
Perhaps I should clarify the problem.
1. the function is NOT tail-recursive
2. Yes, the arguments are immutable after I call the function the
first time.

I think the best description of the problem may be:
How to keep some argument constant and accessable in one function
(especially, recursive function). We know that we can use something
like self.parameter to keep the parameter constant and accessable in
one class.

 

[Diez B. Roggisch]

Assuming the function is tail-recursive or the "unchanging" arguments
are immutable, just use a closure:

[SNIP]
Hi Chris,

Thank you
Perhaps I should clarify the problem.
1. the function is NOT tail-recursive
2. Yes, the arguments are immutable after I call the function the
first time.

I think the best description of the problem may be:
How to keep some argument constant and accessable in one function
(especially, recursive function). We know that we can use something
like self.parameter to keep the parameter constant and accessable in
one class.

The same way chris showed you - using a closure, you can capture
variables outside, and only pass the changing params.

The tail-recursion property isn't needed for that.

Diez