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From: Bob Hanlon on 19 Mar 2010 07:45

expr = b[a[c], a[c], a[d]];

lst = {e, f, g};

Head[expr] @@ Head[expr[[1]]] /@ lst

b[a[e], a[f], a[g]]

More generally,

Inner[Head[#1][#2] &, List @@ expr, lst, Head[expr]]

b[a[e], a[f], a[g]]


Bob Hanlon

---- divisor <congruentialuminaire(a)yahoo.com> wrote:

=============
Hello mathGroup:

I have an expression like this:

b[ a[c], a[c], a[d]]

a list like this:

{e,f,g}

I want to end up with

b[ a[e], a[f], a[g]]

I think of this as interleaving a list into an expression, but all my
tries with ./,.//,MapIndexed[],MapAt[], Partition[Riffle[]] have come
to no avail.

Any help on this is greatly appreciated.

Roger Williams
Franklin Laboratory
http://www.youtube.com/congruentlight


From: rafscipio on 19 Mar 2010 07:45
On 19 Mar, 08:47, divisor <congruentialumina...(a)yahoo.com> wrote:
> Hello mathGroup:
>
> I have an expression like this:
>
> b[ a[c], a[c], a[d]]
>
> a list like this:
>
> {e,f,g}
>
> I want to end up with
>
> b[ a[e], a[f], a[g]]
>
> I think of this as interleaving a list into an expression, but all my
> tries with ./,.//,MapIndexed[],MapAt[], Partition[Riffle[]] have come
> to no avail.
>
> Any help on this is greatly appreciated.
>
> Roger Williams
> Franklin Laboratoryhttp://www.youtube.com/congruentlight

Hi,

here is a way:

In[1]:= x = b[a[c], a[c], a[d]];

In[2]:= y = {e, f, g};

In[3]:= Do[x[[i, 1]] = y[[i]], {i, 3}]; x

Out[3]= b[a[e], a[f], a[g]]


Scipione.

From: rafscipio on 20 Mar 2010 03:46
On 19 Mar, 08:47, divisor <congruentialumina...(a)yahoo.com> wrote:
> Hello mathGroup:
>
> I have an expression like this:
>
> b[ a[c], a[c], a[d]]
>
> a list like this:
>
> {e,f,g}
>
> I want to end up with
>
> b[ a[e], a[f], a[g]]
>
> I think of this as interleaving a list into an expression, but all my
> tries with ./,.//,MapIndexed[],MapAt[], Partition[Riffle[]] have come
> to no avail.
>
> Any help on this is greatly appreciated.
>
> Roger Williams
> Franklin Laboratoryhttp://www.youtube.com/congruentlight

Another variation:

In[1]:= x = b[a[c], a[c], a[d]];

In[2]:= y = {e, f, g};

In[3]:= Evaluate[List@@x[[All, 1]]] = y; x

Scipione

From: Ray Koopman on 20 Mar 2010 04:02
On Mar 19, 4:44 am, Ray Koopman <koop...(a)sfu.ca> wrote:
> On Mar 19, 12:47 am, divisor <congruentialumina...(a)yahoo.com> wrote:
>> Hello mathGroup:
>>
>> I have an expression like this:
>>
>> b[ a[c], a[c], a[d]]
>>
>> a list like this:
>>
>> {e,f,g}
>>
>> I want to end up with
>>
>> b[ a[e], a[f], a[g]]
>>
>> I think of this as interleaving a list into an expression, but all my
>> tries with ./,.//,MapIndexed[],MapAt[], Partition[Riffle[]] have come
>> to no avail.
>>
>> Any help on this is greatly appreciated.
>>
>> Roger Williams
>> Franklin Laboratoryhttp://www.youtube.com/congruentlight
>
> In[1]:= b @@ a /@ {e,f,g}
>
> Out[1]= b[a[e],a[f],a[g]]

Sorry, I misunderstood (oversimplified) the question.
Here is the answer to a slightly more general question.

In[1]:= expr = b[ a[x], c[y], d[z] ];
list = {e, f, g};
Head[expr] @@ MapThread[Head[#1][#2]&,{List@@expr,list}]

Out[3]= b[ a[e], c[f], d[g] ]

From: rafscipio on 20 Mar 2010 04:03
On 19 Mar, 08:47, divisor <congruentialumina...(a)yahoo.com> wrote:
> Hello mathGroup:
>
> I have an expression like this:
>
> b[ a[c], a[c], a[d]]
>
> a list like this:
>
> {e,f,g}
>
> I want to end up with
>
> b[ a[e], a[f], a[g]]
>
> I think of this as interleaving a list into an expression, but all my
> tries with ./,.//,MapIndexed[],MapAt[], Partition[Riffle[]] have come
> to no avail.
>
> Any help on this is greatly appreciated.
>
> Roger Williams
> Franklin Laboratoryhttp://www.youtube.com/congruentlight

Just to add another way:

In[1]:= x = b[a[c], a[c], a[d]];

In[2]:= y = {e, f, g};

In[3]:= Inner[(#1[#2]) &, Level[x[[All, 0]], 1], y, Head@x]

Scipione

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