1. Code generation apparatus used in a computer system to generate machine-executable instructions, the code generation apparatus including at least a text written in a programming language, the text including a definition of a function, and means for generating the machine-executable instructions from the text, the code generation apparatus having the improvement comprising: in the text, a name which has global scope in the text and specifies a value which is separately instantiated for each execution of the function and a use specification which specifies how the name is used in an execution of the function; and in the means for generating the machine-executable instructions, means responsive to the name for making a definition thereof which indicates that the name has global scope and specifies a value which is separately instantiated for each execution of the function; and means responsive to the definition and to the use specification for generating the machine-executable instructions for the function such that when the function is executed, a separate instance of the value represented by the name is created and that instance is used in the execution as specified by the use specification.
2. The apparatus set forth in claim 1 wherein: the instructions are callback code; and the name represents an actual argument for the callback code.