Re: What is f[1]? Advanced question

*To*: mathgroup at smc.vnet.net*Subject*: [mg131306] Re: What is f[1]? Advanced question*From*: "Mannucci, Anthony J (335G)" <anthony.j.mannucci at jpl.nasa.gov>*Date*: Wed, 26 Jun 2013 01:03:30 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net

I believe I figured this out. x[] is a function that has definitions only at certain values. A function can be defined thus: x[x_] := which matches the rhs to a pattern (x_), or a function can be defined thus: x[1] = 0.1 which means: if the function argument expression evaluates to 1, then substitute 0.1. However, if the function argument evaluated to something other than 1, there is no substitution made, so that x[2] just evaluates to x[2]. I don't think there is an Array data type in Mathematica. Thank you! -Tony From: Tomas Garza <tgarza10 at msn.com<mailto:tgarza10 at msn.com>> Date: Tuesday, June 25, 2013 6:27 PM To: Tony Mannucci <Anthony.J.Mannucci at jpl.nasa.gov<mailto:Anthony.J.Mannucci at jpl.nasa.gov>>, "mathgroup at smc.vnet.net<mailto:mathgroup at smc.vnet.net>" <mathgroup at smc.vnet.net<mailto:mathgroup at smc.vnet.net>> Subject: [mg131306] Re: What is f[1]? Advanced question It is possibly a previously declared "Array" with the name "x", and the three lines are assigning values to the elements of the array. Check for Array in the Help. -Tomas > From: Anthony.J.Mannucci at jpl.nasa.gov<mailto:Anthony.J.Mannucci at jpl.nasa.gov> > Subject: What is f[1]? Advanced question > To: mathgroup at smc.vnet.net<mailto:mathgroup at smc.vnet.net> > Date: Tue, 25 Jun 2013 21:14:08 -0400 > > I have found a Mathematica program with the following construct: > x[1]=0.1 > x[2]=0.2 > x[3]=0.3 > > or > Do[x[i]=i/10.,{i,1,3}] > > x is not a function. It is not a list. What is it? If I query x thus: > ?x > > the answer is just what I have written above. Mathematica knows about x[1], x[2], etc. How does Mathematica know about the "elements" of x? > > In some other sense, I could have written: > y1 = 0.1 > y2 = 0.2 > y3 = 0.3 > > But > ?y > > obviously gives a different result (just returns y). > > Thank you. >