Lustre (programming language)

Lustre is a formally defined, declarative, and synchronous dataflow programming language for programming reactive systems. It began as a research project in the early 1980s. A formal presentation of the language can be found in the 1991 Proceedings of the IEEE.^[1] In 1993 it progressed to practical, industrial use in a commercial product as the core language of the industrial environment SCADE, developed by Esterel Technologies. It is now used for critical control software in aircraft,^[2] helicopters, and nuclear power plants.

Structure of Lustre programs

An Lustre program is a series of node definitions, written as:

node foo(a : bool) returns (b : bool);
let
  b = not a;
tel

Where foo is the name of the node, a is the name of the single input of this node and b is the name of the single output. In this example the node foo returns the negation of its input a which is the expected result.

Inner variables

Additional variables can be declared as follow:

 node Nand(X,Y: bool) returns (Z: bool);
   var U: bool;
 let
   U = X and Y;
   Z = not U;
 tel

Note: The equations order doesn't matter, the order of lines U = X and Y; and Z = not U; doesn't change the result.

Special operators

`pre` p	Return the last value of p
p `->` q	Set p as the initial value of the expression q

Examples

Edge detection

node Edge (X : bool) returns (E : bool);
let
  E = false -> X and not pre X;
tel

References

^ [1] N. Halbwachs et al. The Synchronous Data Flow Programming Language LUSTRE. In Proc. IEEE 1991 Vol. 79, No. 9. Accessed 17 March 2014.
^ "SCADE Success Stories". Retrieved 8 June 2013.

External links

Synchrone Lab Official website
SCADE product page

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[1] [1] N. Halbwachs et al. The Synchronous Data Flow Programming Language LUSTRE. In Proc. IEEE 1991 Vol. 79, No. 9. Accessed 17 March 2014.

[2] "SCADE Success Stories". Retrieved 8 June 2013.

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