Question about thread

*To*: mathgroup at smc.vnet.net*Subject*: [mg2581] Question about thread*From*: sherod at boussinesq.Colorado.EDU (Scott Herod)*Date*: Mon, 27 Nov 1995 21:31:00 -0500*Organization*: University of Colorado at Boulder

I have a question about the way Thread behaves. From the description in the _Mathematica_ book, I would expect it to return lists. For example Mathematica 2.2 for Solaris Copyright 1988-93 Wolfram Research, Inc. License valid through 28 Nov 1995. -- Open Look graphics initialized -- In[1]:= Thread[f[{a,b},x]] Out[1]= {f[a, x], f[b, x]} But that doesn't always seem to be the case. In[2]:= blat[p_, q_] := Module[{}, Plus @@ (Variables[p]^q)] In[3]:= blat[a+b,x] x x Out[3]= a + b In[4]:= Thread[blat[{a+c,b+d},x]] x x x x Out[4]= a + b + c + d Why isn't Out[4] the same as In[5]:= Outer[blat, {a+c, b+d} , {x}] // Flatten x x x x Out[5]= {a + c , b + d } Scott Herod Applied Mathematics University of Colorado, Boulder sherod at colorado.edu