Lustre (programming language)

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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[edit]

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

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

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[edit]

Additional internal variables can be declared as follows:

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

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[edit]

pre p Returns the previous value of p
p -> q Set p as the initial value of the expression q


Edge detection[edit]

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

See also[edit]


  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.

External links[edit]