Sergey Dorofeev wrote: > "Peter Otten" <[EMAIL PROTECTED]> wrote in message > news:[EMAIL PROTECTED] >> Sergey Dorofeev wrote: >> >>> Please help, is there way to use sub-expressions in lambda? >>> For example, if I want to calculate sin(x^2)+cos(x^2) I must code: >>> lambda x: sin(x*x)+cos(x*x) >>> How to make x*x to be evaluated once? >>>>> (lambda x: [sin(x2) + cos(x2) for x2 in [x*x]][0])(.5) == sin(.5*.5) + >> cos(.5*.5) >> True >> >> The real answer is of course: Use a function. > > But what about something like > > lambda x: sin(y)+cos(y) where y=x*x > > ? > May be this could be a PEP? If there is no straight way to do this. > > Or maybe it could be made a part of some other language. When straightforward mechanisms (in rhis case, function definitins) exist to avoid repeated computations it's very unlikely that such mangled constructions will be made a part of Python.
If it *were* considered, you should at least change the "where" to "for", and extend it to unpacking assignment to allow lambda x, y: (sin(xx+yy) + cos(xx+yy) for xx, yy = x*x, y*y regards Steve -- Steve Holden +1 571 484 6266 +1 800 494 3119 Holden Web LLC/Ltd http://www.holdenweb.com Skype: holdenweb http://del.icio.us/steve.holden ------------------ Asciimercial --------------------- Get on the web: Blog, lens and tag your way to fame!! holdenweb.blogspot.com squidoo.com/pythonology tagged items: del.icio.us/steve.holden/python All these services currently offer free registration! -------------- Thank You for Reading ---------------- -- http://mail.python.org/mailman/listinfo/python-list