lazy evaluation

Concept

Call-by-need - evaluation of an expression is delayed until its value is needed

Allows for:

• control flow as abstractions instead of primitives
• defining potentially infinite data structures(streams)
• partly define data structures, in which some elements may be errors

Application

Control flow

function recur(x) {
	return x || recur(true); // Iterative Process
}

recur(true);  // -> True : immediately returns true
recur(false); // -> True : function is called once recursively, since x if false the first time

Infinte/circular stream

const ones = pair(1, () => ones);

head(ones); // -> 1
head(streamm_tail(ones)); // -> 1