Distributed Systems Playground

A program contains interfaces and algorithms. An algorithm implements one interface and uses others: Net (network) and Rounds (synchronous rounds) are provided by the simulator; the rest you write yourself, and they are wired together automatically.

upon event ⟨instance, Event | pattern⟩ where condition do … end
upon condition expression do … end
upon exists x in S where condition do … end
trigger ⟨instance, Event | arg1, arg2⟩
forall q in neighbors where q ≠ p do … end
if … then … elif … then … else … end
starttimer(t, 100ms)   canceltimer(t)
⟨timer, Timeout | t⟩   assert cond, "msg"   log x

function name(a, b) … return value … end      call name(x, y)
uses PerfectLinks as pl via AckLinks

Functions live inside an algorithm, see its state and parameters, and may trigger events; use them in expressions, or with call as a statement. via picks which algorithm implements a used interface when there are several.

Indications go up, requests go down. Undeclared all-caps words (HEARTBEAT) are atoms. In patterns, a new name captures the value; an atom or a known name must match.

Built-ins: self, Π, N, neighbors, round, now(), DELTA PHI RHO (only when known in the assumed model), min max choose size keys values map() get(m,k,default) remove(c,x) random(a,b) pick(S) append head tail last sort reverse slice range sum mean argmin argmax toset str abs sqrt ln exp pow floor ceil round. Tuples are 0-indexed; #S is the cardinality. Durations (50ms) are numbers in microseconds.

ASCII equivalents: < > for ⟨ ⟩, union inter minus in notin subseteq, != <= >=, and or not, Procs for Π, {} for ∅. Inside an ASCII trigger, wrap comparisons in parentheses.