Re: basic issue with do and :=

*To*: mathgroup at smc.vnet.net*Subject*: [mg60426] Re: basic issue with do and :=*From*: dh <dh at metrohm.ch>*Date*: Fri, 16 Sep 2005 03:49:06 -0400 (EDT)*References*: <dgbevg$fol$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi David, this may be confusing, but it is correct. Consider: Do[b[i] :=a[i]+1, {i, 10}] As you can read in the manual, Do temporarily sets i to 1,2..., effectively using Block. Outside Do, i has the original value. However, := does not evaluate its right hand side, but stores it in unevaluated form. When you later use b[i], i is evaluated to whatever value it has at this time. sincerely, Daniel David wrote: > Hi all, > > this works as (I) expected > > ------------------------- > Do[a[i] = i, {i, 10}] > Do[b[i] =a[i]+1, {i, 10}] > ------------------------- > > While this doesn't: > > -------------------------- > Do[a[i] = i, {i, 10}] > Do[b[i] :=a[i]+1, {i, 10}] > --------------------------- > > [note ":=" instead of "=" on the second line]. > > namely the output is: "b[2]:=a[i]+1" for all i > > > > Is there any compact way to define: "b[i] :=a[i]+1" for all i ? > > > Thank you in advance, > > David >