Re: V6 evaluation inside Table and plot

*To*: mathgroup at smc.vnet.net*Subject*: [mg76670] Re: V6 evaluation inside Table and plot*From*: Vince Virgilio <blueschi at gmail.com>*Date*: Fri, 25 May 2007 06:44:27 -0400 (EDT)*References*: <f33onq$l4v$1@smc.vnet.net>

On May 24, 6:17 am, Gerry Flanagan <flana... at materials-sciences.com> wrote: > Define a simple function > > In[7]:= f = Function[{x}, x^3] > > Out[7]= Function[{x}, x^3] > > Taking two derivatives works as it should > > In[2]:= f''[x] > > I was converting some packages to work with V6, and immediately ran into > some evaluation issues I don't understand. It looks like forms like > f''[x] (derivative) are evaluated differently inside of Table and Plot > than outside. > > Out[2]= 6 x > > But this does not? > > In[20]:= Table[f''[x], {x, 0, 1, .2}] > > Out[20]= {0, 0, 0, 0, 0, 0} > > Strangely, this works > > In[4]:= Table[f'[x], {x, 0, 1, .2}] > > Out[4]= {0., 0.12, 0.48, 1.08, 1.92, 3.} > > Determining the derivative outside the Table makes it work again. > > In[12]:= g = f''; > > In[21]:= tmp = Table[g[x], {x, 0, 1, .2}] > > Out[21]= {0., 1.2, 2.4, 3.6, 4.8, 6.} > > Gerry Flanagan Some more food for thought about the evaluator. I had two identical names in two different contexts; one used the other, safely, I thought. I never noticed erroneous behavior with that call sequence in version 5.2. Not so in version 6. I had to eliminate one of the names to successfully run essentially the same code. (Sorry that I can't report more detail on this.) This makes me wonder if there has been an important invisible change in Mathematica's evaluator, that is catching "non-compliant" code. Perhipherally related to this peripheral is my frequent use of relative names, that begin with a context mark. I find they interfere with the Workbench editor parser (mouseovers on relatively-defined names don't give usage messages), and likely the new package editor (can't jump to any function names---relative names are present---still need to disambiguate). The name resolution I allude to above depended on relative names. Vince Virgilio