21.3 Quoted Expressions

Because symbolic evaluation requires that each variable or expression has a value, it is necessary to add to REDUCE the concept of a quoted expression by analogy with the Lisp quote function. This is provided by the single quote mark ’. For example,

’a	represents the Lisp S-expression	(quote a)
’(a b c)	represents the Lisp S-expression	(quote (a b c))

Note, however, that strings are constants and therefore evaluate to themselves in symbolic mode. Thus, to print the string "A String", one would write

        prin2 "A String";

Within a quoted expression, identifier syntax rules are those of REDUCE. Thus (a !. b) is the list consisting of the three elements a, ., and b, whereas (a . b) is the dotted pair of a and b.

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