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,

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

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.