The original Objective-C as shown in Brad Cox's book "Object-Oriented Programming: An Evolutionary Approach" (1986). Note the differences from the present-day version.

Graph.m

// Dependency graph
#include "objc.h"
extern id Node;

= Graph:Set { }

// Add a new node
- addNode:(STR)aCharPointer
    { return [self filter:[Node str:aCharPointer]]; }

// Add a new node and define it
- defineNode:(STR)aCharPointer
    { return [[self addNode:aCharPointer] define]; }

// Mark the given node )and all nodes referenced by it)
- mark:(STR)aNodeName
    { return [[self addNode:aNodeName] mark]; }

=;