Re: How to Return from within a Table[]-Command?

*To*: mathgroup at smc.vnet.net*Subject*: [mg33760] Re: [mg33728] How to Return from within a Table[]-Command?*From*: BobHanlon at aol.com*Date*: Thu, 11 Apr 2002 02:14:18 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

In a message dated 4/10/02 1:57:52 AM, dmueller at mathematik.uni-kassel.de writes: >I wanted to scan trough al List, building a new >List, but aborting, if one Element of the first >List violates a special Condition ... >say for example: > >Divide2[L_List] := Module[{}, > Table[ > If[IntegerQ[L[[i]]], > i/2, > Return["vector not valid."]; > ] > , {i, 1, Length[L]} > ] > > ... > > ] > >But this results: > >In[13]:= Divide2[{2,3,a}] >Out[13]= {1/2, 1, Return["vector not valid."]} > >Wich is of course not what I want. > Throw and Catch work Clear[divide2]; divide2[lst_?VectorQ] := Module[{i=1}, Catch[If[IntegerQ[#], i++/2, Throw["vector not valid"]]& /@ lst]]; divide2[{2,3,6}] {1/2, 1, 3/2} divide2[{2,3,a}] "vector not valid" However, if all you want to verify is some test of the elements then a pattern will work and is more efficient since it does not do any evaluations unless the results are needed Clear[divide2]; divide2[x:{__Integer}] := Range[Length[x]]/2; divide2[x_] := "vector not valid"; divide2[{2,3,6}] {1/2, 1, 3/2} divide2[{2,3,a}] "vector not valid" Bob Hanlon Chantilly, VA USA