# perimeter #
MODE V = [2]REAL;
[] V vt = ((-1, -1), (1, -1), (1, 1), (-1, 1), (-2, 0.3));
PROC dp = (V a, V b)REAL:
  (REAL ss := 0; FOR j TO UPB a DO ss +:= a[j]*b[j] OD; ss);
PROC leng = (V v)REAL: sqrt(dp(v, v));
OP - = (V a, V b)V: (V c; FOR j TO UPB a DO c[j] := a[j] - b[j] OD; c);
OP * = (REAL b, V a)V: (V c; FOR j TO UPB a DO c[j] := a[j]*b OD; c);
(PROC ie = (INT i, j)REAL: (PROC ise = (INT i, j)REAL:
    (V tt = (vt[j] - vt[i]); dp(vt[i], (1.0/leng(tt))*tt));
  ise(i, j)+ise(j, i));
# Mysterious formula: #
(REAL tv := ie(UPB vt, 1); FOR j TO UPB vt - 1 DO tv +:= ie(j, j+1) OD;
print(tv)));
# Conventional formula: #
(REAL ss := leng(vt[1]-vt[UPB vt]);
  FOR j TO UPB vt - 1 DO ss+:= leng(vt[j]-vt[j+1]) OD; print (ss))