Using "=" vs ":="
- To: mathgroup at smc.vnet.net
- Subject: [mg70664] Using "=" vs ":="
- From: misha <iamisha1 at comcast.net>
- Date: Sun, 22 Oct 2006 01:20:22 -0400 (EDT)
I'm going through Mathematic by Example, 2nd ed., (Abell and Braselton), and have come across something that puzzles me. Chapter 2, Section 2, Example 8 Define f(x,y)=1-sin(x^2+y^2) So I first try, In[1]:= f[x_, y_]:=1-Sin(x^2+y^2) No problem so far... Then, In[2]:= f[x,y] Out[2]:=1-Sin(x^2+y^2) Still no problem... Then, In[3]:=f[1,2] Out[3]:=1-5 Sin Huh? I noticed that rather than using ":=" to "simply define" this function, as opposed to (just) "=" to "define and compute" this function, I get different subsequent behavior. Specifically, doing the above with just "=", works fine. In[1]:= f[x_, y_]=1-Sin(x^2+y^2) .... In[3]:=f[1,2] Out[3]:=1-Sin[5] My question is, Why? What's the difference between ":=" and "=" for defining functions? Thanks! Misha
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