Spaces Spaces are ignored by the interpreter. Debugging The debugging trace and stack dumps are turned on and off by debug bool . This feature is not part of the language described in Dijkstra's book. Semicolons Semicolons separate items in a list, but do not terminate lists. Blocks A program must be enclosed in a block.
Blocks also delimit variable scope within the main program.
A block starts with a list of variable names and their scope. It can be variable or constant. Each guard evaluates to true or false. A consequence following a false guard will not be evaluated. The do statement will repeat until no guard is true.