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.