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lv6-ref-man/objpdf/speed.lus.github.tex

+
+% Automatically generated by utils/lus2tex
+% from file /home/jahier/github/lustre-examples/verimag-v6/examples//speed.lus scriptsize
+% the jeudi 11 juin 2020, 08:39:55 (UTC+0200)
+
+\begin{minipage}{\textwidth}
+\begin{scriptsize}
+\begin{alltt}
+
+\coment{-- Time-stamp: <modified the 11/06/2020 (at 08:39) by Erwan Jahier> }
+\coment{-- Computes the speed (of some vehicle \kwdd{with} wheels) out of 2 sampled inputs:}
+\coment{-- + Rot, \kwdd{true} iff the wheel has performed a comp\kwd{let}e rotation}
+\coment{-- + Tic, \kwdd{true} iff some external clock has emitted a signal indicating that }
+\coment{--        some \kwd{const}ant amount of time elapsed (e.g., 100 ms)  }
+\coment{--}
+\coment{-- This example was inspired from a \kwdd{real} program in a train regulating system}
+\kwd{const} period = 0.1;  \coment{-- in seconds}
+\kwd{const} wheel_girth = 1.4;  \coment{-- in meter}
+\kwd{const} size = 20; \coment{-- size of the sliding window used to compute the speed}
+\kwd{node} compute_speed(Rot, Tic: \kwdd{bool}) \kwd{returns} (Speed:\kwdd{real});
+var  d,t,dx,tx:\kwdd{real};
+\kwd{let}
+  dx = \kwdd{if} Rot \kwdd{then} wheel_girth \kwdd{else} 0.0;
+  tx = \kwdd{if} Tic \kwdd{then} period \kwdd{else} 0.0;
+  d = sum<<size,0.0>>(dx);
+  t = sum<<size,period>>(tx);
+  \coment{-- the speed is actually the average speed during the last "size*period" seconds  }
+  Speed = (d/t);
+  \coment{-- nb : yes there can be some division by zero! For instance \kwdd{if} the vehicle}
+  \coment{-- overtakes the speed of size*wheel_girth/period}
+  \coment{-- (i.e., \kwdd{with} size=20, period=0.1, wheel_girth=1.4, \kwdd{if} the speed is > 1008km/h)}
+  \coment{-- This means that for high-speed vehicle, one \kwddd{needs} to increase "size".}
+\kwd{tel}
+\coment{-- The idea is to call the \kwd{node} that do the computation only \kwd{when} needed, i.e.,}
+\coment{-- \kwd{when} Tic \kwdd{or} Rot is \kwdd{true}. }
+\kwd{node} speed(Rot, Tic: \kwdd{bool}) \kwd{returns} (Speed:\kwdd{real});
+var
+  TicOrRot : \kwdd{bool};
+  NewSpeed : \kwdd{real} \kwd{when} TicOrRot;
+\kwd{let}
+  TicOrRot = Tic \kwdd{or} Rot;
+  NewSpeed = compute_speed(Rot \kwd{when} TicOrRot, Tic \kwd{when} TicOrRot);
+  Speed = current(NewSpeed);
+\kwd{tel}
+\coment{-- computes the sum of the last d values taken by s}
+\kwd{node} sum<<\kwd{const} d: \kwdd{int}; const init:\kwdd{real}>>(s: \kwdd{real}) \kwd{returns} (res:\kwdd{real});
+var
+  a,pre_a: \kwdd{real}^d; \coment{-- circular array}
+  i: \kwdd{int}; 
+\kwd{let}
+  i = 0 fby i + 1;
+  pre_a = (init^d) fby a;
+  a = assign<<d>>(s, i mod d, pre_a);
+  res =red<<+; d>>(0.0, a); 
+\kwd{tel}
+\coment{-- assign the jth element of an array to a value. v.(j) <- i}
+\kwd{type} update_acc = \{ i: \kwdd{int}; j: \kwdd{int}; v: \kwdd{real} \};
+\kwd{function} update_cell_do<<\kwd{const} d: \kwdd{int}>>(acc: update_acc; cell: \kwdd{real}) 
+\kwd{returns} (nacc: update_acc; ncell: \kwdd{real});
+\kwd{let}
+  ncell = \kwdd{if} acc.i = acc.j \kwdd{then} acc.v \kwdd{else} cell;
+  nacc = update_acc \{ i = acc.i+1; j = acc.j ; v = acc.v \};
+\kwd{tel}
+\kwd{function} assign<<\kwd{const} d: \kwdd{int}>>(v: \kwdd{real}; jv: \kwdd{int};  t: \kwdd{real}^d) \kwd{returns} (nt: \kwdd{real}^d)
+var
+  dummy: update_acc; 
+\kwd{let}
+  dummy, nt=fillred<<update_cell_do<<d>>; d>>( update_acc \{ i=0 ; j=jv ; v=v \}, t);
+\kwd{tel}
+\end{alltt}
+\end{scriptsize}
+\end{minipage}
+