Re: strange behavior with Map

*To*: mathgroup at smc.vnet.net*Subject*: [mg116398] Re: strange behavior with Map*From*: Leonid Shifrin <lshifr at gmail.com>*Date*: Sun, 13 Feb 2011 03:07:07 -0500 (EST)*References*: <201102121020.FAA20181@smc.vnet.net>

Hi Robert, It's a bit subtle indeed. The key observation is this: In[23]:= Map[f, {{1, 2}, {1, 2}}, 2] Out[23]= {f[{f[1], f[2]}], f[{f[1], f[2]}]} Since things evaluate from the bottom, the interesting part happens after we have this: {f[{2, 2}], f[{2, 2}]} (schematically - in reality, the first f completely evaluates, and only then the second). Now, consider: In[27]:= Function[x, 0 x + 2][{2, 2}] Out[27]= {2, 2} In[28]:= Function[x, 2][{2, 2}] Out[28]= 2 which is, the functions *are* different, because multiplication by a scalar (zero included) preserves the dimensionality of the second factor, for the first function, while the second function simply replaces the argument by 2, whatever it is. Regards, Leonid On Sat, Feb 12, 2011 at 1:20 PM, Robert Rosenbaum <robertr at math.uh.edu>wrote: > This doesn't seem right: > > > In[181]:= Map[Function[x, 2], {{1, 2}, {1, 2}}, 2] > > Out[181]= {2, 2} > > In[180]:= Map[Function[x, 0 x + 2], {{1, 2}, {1, 2}}, 2] > > Out[180]= {{2, 2}, {2, 2}} > > > Best, > Robert > >

**References**:**strange behavior with Map***From:*Robert Rosenbaum <robertr@math.uh.edu>