Re: beginner question about syntax

*To*: mathgroup at smc.vnet.net*Subject*: [mg109088] Re: beginner question about syntax*From*: Mike Bryniarski <melondisco at gmail.com>*Date*: Mon, 12 Apr 2010 22:59:42 -0400 (EDT)*References*: <hputp3$lh7$1@smc.vnet.net>

For map to work you must be mapping over the elements of an expression, be it a list like {a,b,c} or a generic expression like f[a,b,c] in your first example : Map[Function[x, x^2], a] a is an atomic symbol, Map normally tries to apply the function to level one of the expression but "a" has no level 1 this fails, what you would want to use is: Function[x, x^2][a] In your second example what is going on is that a+b+c is really seen by Mathematica as Plus[a,b,c], so Map[Function[x, x^2], a + b + c] is really Map[Function[x, x^2],Plus[a,b,c]] and the function is applies to each element of the Plus statement while keeping Plus as the "head" of the expression an intermediate step might look something like: Plus[Function[x, x^2][a],Function[x, x^2][b],Function[x, x^2][c]] which becoms: Plus[a^2,b^2,c^2] or: a^2+b^2+c^2 -Mike On Apr 12, 6:48 am, AK <aaa... at googlemail.com> wrote: > Hi, > > I'm a fairly seasoned user of another system who's just started using > Mathematica. Although at the moment I'm just playing around with > Mathematica (without any specific task at hand), trying to figure out > the Mathematica way of doing things from the documentation > (particularly the examples) there are some things I can't seem to wrap > my head around. For example, can anyone explain the outputs for the > inputs below: > In[1]:= Map[Function[x, x^2], a] > Out[1]:= a > In[2]:=Map[Function[x, x^2], a + b + c] > Out[2]:= a^2 + b^2 + c^2 > > If I enclose the second argument of Map[] inside a list, I get the > expected output, but I don't understand what the operations given in > the example above represent and why the outputs are what they are. > Would appreciate an explanation for what's going here... thank you in > advance.