Lars Hellström <[log in to unmask]> writes:



>   \@fancyfor\@tempa:=<list>\do{\@tempa}{, \@tempa}{ and \@tempa}

> and for <list> equal to A; A,B; A,B,C; A,B,C,D respectively get the results

>   A

>   A and B

>   A, B and C

>   A, B, C and D



As it happens I was working on similar functionality recently for the

amsrefs package (ftp://ftp.ams.org/pub/tex/amsrefs.zip). The package has

a \PrintSeries function used to print author names in a bibliography

when the data is a list of names in the form



  \name{Downes, Michael}\name{Hellström, Lars}...



For AMS conventions your first/middle/last approach is not quite

adequate because cases 2 and 3 must be printed as



  A and B

  A, B, and C         (Note the extra comma.)



And there are some other complications, as explained in the following

commentary from amsrefs.dtx:



%    The \cn{PrintSeries} command prints a list of objects in series

%    form. The essential idea is to produce something like \qq{A, B, and

%    C} when we are given three elements A B C, with suitable variations

%    in the punctuation and other intervening material if the number of

%    elements is less or more than three.

%

%    To generalize this process, we envision \cn{PrintSeries} being

%    called as



%\PrintSeries{i0}{i1}{i2}{i3}{i4}{\do{A}\do{B}...}



%    where i0, \dots, i4 are material to be interpolated and the last

%    arg is a list of indeterminate length where each element consists

%    of a macro and its argument. The output, depending on the number of

%    elements, will be



% i0 A i4                 % 1 element

% i0 A i1 B i4            % 2 elements

% i0 A i2 B i3 C i4       % 3 elements

% i0 A i2 B i2 C i2 ... X i2 Y i3 Z i4   % 26 elements



%    That is the simple explanation but in practice there are some

%    additional complications. What if user-supplied line breaks have to

%    be supported at the boundaries between elements? What if in

%    addition to adding material between elements we also want to apply

%    some handy function to each element (e.g., \cn{textsc})? Even

%    worse, what if we want the function to be different depending on

%    the position of the element in the list?? Indeed if this did not

%    happen to be the case with the current application I would not have

%    gone to the extra trouble of supporting it. But if it must be so,

%    then the output that we need from a list \verb'\do{A}\do{B}...' is



% f0{A}

% f0{A} p1 i1 f1{B}

% f0{A} p2 i2 f2{B} p3 i3 f3{B}



%    and so on, where

% \begin{itemize}

% \item $f_n$ is a macro taking one argument,

% \item $p_n$ is punctuation\mdash material that must precede a line

%    break if one occurs at this boundary,

% \item $i_n$ other interpolated material, as before.

% \end{itemize}

%    To reduce the number of distinct required objects we decree that

%    each element will get braces wrapped around it as a matter of

%    course; then it is possible for f1, f2, f3 to be assimilated into

%    the tail end of i1, i2, i3.