Therefore, there must be a way to define true and false
independently from the functions true() and false() -- this
definition must provide a means to determine if a given value
"is the value true or is the value false" without referencing
functions, which themselves are defined using the values true
and false.
This problem applies to all the data types. How can one define what
integers are without using external representations of their values? At
heart, it's a problem for pure mathematicians. In an engineering
specification, I think one is entitled to assume that integers and
booleans exist, and to incorporate them by reference. You should regard
"true" and "false" as references to these basic concepts, rather than as
tokens in the language used to represent them.
Michael Kay
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