There are three commands in the Sling language: plot, assignment, and for. The for command is syntactically different from a Java for command, but its function is similar. The plot command and the assignment command need application-specific implementations in sjm.examples.sling.
This command encapsulates a user's plot command. Internally, the Sling parser does not actually start drawing when it parses a plot command. Rather, the parser uses an assembler to place an AddFunctionCommand object on an assembly's stack. Figure 16.22 shows AddFunctionCommand.