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Re: Adding the elements of a list sequentially

  • To: mathgroup at smc.vnet.net
  • Subject: [mg109349] Re: Adding the elements of a list sequentially
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 23 Apr 2010 03:47:12 -0400 (EDT)

Your first example does not seem to be consistent with what you described.

f[a_?VectorQ, b_?VectorQ] := a + PadRight[b, Length[a], b];

a = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

b = {1, 2};

f[a, b]

{2,4,4,6,6,8,8,10,10,12}

f[b, a]

{2,4}

a = {1, 1, 1, 1, 1};

b = {1, 2, 3};

f[a, b]

{2,3,4,2,3}

f[b, a]

{2,3,4}


Bob Hanlon

---- ebaugh at illinois.edu wrote: 

=============
I am looking for an efficient way to add the elements of a list 
sequentially onto another list

For example, generate list c, given lists a and b:

a = {1,2,3,4,5,6,7,8,9,10}
b = {1,2}

c = {2,4,4,5,6,7,8,9,10,11}


another example:

a = {1,1,1,1,1}
b = {1,2,3}

c = {2,3,4,2,3}

It seems like there must be a built in function to do this, but 
have been unable to find it.


Thanks a 10^6
Jason Ebaugh




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