6.2 Nouns and Verbs

Maxima distinguishes between operators which are "nouns" and operators which are "verbs". A verb is an operator which can be executed. A noun is an operator which appears as a symbol in an expression, without being executed. By default, function names are verbs. A verb can be changed into a noun by quoting the function name or applying the nounify function. A noun can be changed into a verb by applying the verbify function. The evaluation flag nouns causes ev to evaluate nouns in an expression.

The verb form is distinguished by a leading dollar sign $ on the corresponding Lisp symbol. In contrast, the noun form is distinguished by a leading percent sign % on the corresponding Lisp symbol. Some nouns have special display properties, such as 'integrate and 'derivative (returned by diff), but most do not. By default, the noun and verb forms of a function are identical when displayed. The global flag noundisp causes Maxima to display nouns with a leading quote mark '.

See also noun, nouns, nounify, and verbify.

Examples:

(%i1) foo (x) := x^2;
                                     2
(%o1)                     foo(x) := x

(%i2) foo (42);
(%o2)                         1764

(%i3) 'foo (42);
(%o3)                        foo(42)

(%i4) 'foo (42), nouns;
(%o4)                         1764

(%i5) declare (bar, noun);
(%o5)                         done

(%i6) bar (x) := x/17;
                                    x
(%o6)                     bar(x) := --
                                    17

(%i7) bar (52);
(%o7)                        bar(52)

(%i8) bar (52), nouns;
(%o8)                        bar(52)

(%i9) integrate (1/x, x, 1, 42);
(%o9)                        log(42)

(%i10) 'integrate (1/x, x, 1, 42);
                             42
                            /
                            [   1
(%o10)                      I   - dx
                            ]   x
                            /
                             1

(%i11) ev (%, nouns);
(%o11)                       log(42)