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Is

Function: is (<expr>) Attempts to determine whether the predicate <expr> is provable from the facts in the assume database.

If the predicate is provably true or false, is returns true or false, respectively. Otherwise, the return value is governed by the global flag prederror. When prederror is true, is complains with an error message. Otherwise, is returns unknown.

ev(<expr>, pred) (which can be written <expr>, pred at the interactive prompt) is equivalent to is(<expr>).

See also assume, facts, and maybe.

Examples:

is causes evaluation of predicates.

          (%i1) %pi > %e;
          (%o1)                       %pi > %e
          (%i2) is (%pi > %e);
          (%o2)                         true

is attempts to derive predicates from the assume database.

          (%i1) assume (a > b);
          (%o1)                        [a > b]
          (%i2) assume (b > c);
          (%o2)                        [b > c]
          (%i3) is (a < b);
          (%o3)                         false
          (%i4) is (a > c);
          (%o4)                         true
          (%i5) is (equal (a, c));
          (%o5)                         false

If is can neither prove nor disprove a predicate from the assume database, the global flag prederror governs the behavior of is.

          (%i1) assume (a > b);
          (%o1)                        [a > b]
          (%i2) prederror: true$
          (%i3) is (a > 0);
          Maxima was unable to evaluate the predicate:
          a > 0
           -- an error.  Quitting.  To debug this try debugmode(true);
          (%i4) prederror: false$
          (%i5) is (a > 0);
          (%o5)                        unknown

There are also some inexact matches for is. Try ?? is to see them.

(%o1)                                true
(%i2)