Chapter 1  Synchronous Programming

This chapter and the next one give a tutorial introduction to Zélus. This chapter focuses on the synchronous kernel of the language, which is reminiscent of Lustre and Lucid Synchrone. We shall sometimes compare Zélus with those two languages. The next chapter focuses on newer, hybrid aspects, like ODEs, zero-crossings, and their interaction with the synchronous features. The simulation engine is described in chapter 3.

Familiarity with general programming languages is assumed. Some familiarity with (strict or lazy) ML languages and with existing synchronous data-flow languages like Lustre is helpful but not mandatory. Some references are given at the end of this document.

In this tutorial, we suppose that programs are written in a file called tutorial.zls.

• The Core Synchronous Language
  • Point-wise Operations
  • Delays
  • Global Declarations
  • Combinatorial Functions
  • Stateful Functions
  • Local and Mutually Recursive Definitions
  • Shared Memory and Initialization
  • Causality Check
  • Initialization Check
• Data types and Pattern Matching
  • Type Definitions
  • Pattern Matching
  • Pre versus Last
  • Local Definitions
  • Implicit Completion of Shared Variables
• Valued Signals
  • Signal Emission
  • Signal Presence and Values
• Hierarchical State Machines
  • Strong Preemption
  • Weak Preemption
  • Parameterized States
  • Modular Resets
  • Local State Definitions
  • States and Shared Memory
  • The Initial State
  • Resuming a State
  • Actions on Transitions
  • Signals and State Machines
  • Pattern Matching over Signals
• Alternative Syntax for Control Structures
• Real Time versus Logical Time