Can you draw a path from a list or otherwise avoid piecewise joint declarations? (In metapost)

Here's one possibility with metapost. For a macro to take an array as an argument, it is declared as a suffix argument, i.e. one that has suffixes which in this case are 0,1,2,.... The input array must start with index/suffix 0.

\documentclass[border=10cm]{standalone}
\usepackage{luamplib}

\begin{document}
\begin{mplibcode}
vardef pairs(suffix P)=
    save p_,i_; path p_;
    i_:=0;
    p_:=P[0] forever: exitif not (known P[incr i_]); --P[i_] endfor;
    p_
enddef;

beginfig(0);
u:=1cm;
pair p[];
p[0]=origin;
p[1]=u*(1,1);
p[2]=u*(2,0);
p[3]=u*(4,0);

draw pairs(p) withpen pencircle scaled 1bp withcolor red;
endfig;
\end{mplibcode}

\end{document}

Edit: As per Thruston's suggestion, we can be a bit more general here. If you would like the option of straight segments or Bezier curves then you could use:

\begin{mplibcode}
vardef pairs(suffix P)(text joiner)=
    save p_,i_; path p_;
    i_:=0;
    P[0] forever: exitif not (known P[incr i_]); joiner P[i_] endfor
enddef;

beginfig(0);
u:=1cm;
pair p[];
p[0]=origin;
p[1]=u*(1,1);
p[2]=u*(2,0);
p[3]=u*(4,-1);
drawoptions(withpen pencircle scaled 1bp);
draw pairs(p,..) withcolor red;
draw pairs(p,--) withcolor blue;
draw pairs(p,{right}..{right});
%k:=0;
%draw pairs(p,{dir (incr k*30)}..{right}) withcolor green;
drawoptions();

endfig;
\end{mplibcode}

Since many TikZ answers get MetaPost answers (which is of course great) here is a TikZ answer for this presumably MetaPost question. Given a list, say, \def\mylist{(0,1) (1,2) (2.5,1/2)} it is very well known that you can plot this list with \draw[blue] plot[smooth] coordinates {\mylist};. What is somewhat less known is that you can also plot lists which have the Mathematica/C++ array structure, say, \def\mylist{{0,1},{1,2},{2.5,1/2}}. This works by exploiting that TikZ can parse and access arrays,

\draw plot[samples at={0,1,2}] ({{\mylist}[\x][0]},{{\mylist}[\x][1]});

Full MWE with smooth examples:

\documentclass[tikz,margin=3]{standalone}
\begin{document}
\begin{tikzpicture}
\def\mylist{(0,1) (1,2) (2.5,1/2)}
\draw plot coordinates {\mylist};
\draw[blue] plot[smooth] coordinates {\mylist};
\begin{scope}[yshift=-4cm]
\def\mylist{{0,1},{1,2},{2.5,1/2}}
\draw plot[samples at={0,1,2}] ({{\mylist}[\x][0]},{{\mylist}[\x][1]});
\draw[blue] plot[smooth,samples at={0,1,2}] ({{\mylist}[\x][0]},{{\mylist}[\x][1]});
\end{scope}
\end{tikzpicture}
\end{document}