Primitive Functions

• (MS x) moves x to the top of the stack and returns T otherwise does nothing and returns F,
• (MT x) if block x is in the stack it moves the top block off the stack and puts it on the table and returns T otherwise it does nothing and returns F,
• (EQ x y) returns T if x=y and returns F otherwise
• (Not x) returns T if x = F and F if x = T
• (Du x y) executes the expression x repeatedly until y returns the value T