### The Maxima on-line user's manual

Algebra Calculator

#### Evflag

-- Property: evflag When a symbol <x> has the `evflag` property, the expressions `ev(<expr>, <x>)` and `<expr>, <x>` (at the interactive prompt) are equivalent to `ev(<expr>, <x> = true)`. That is, <x> is bound to `true` while <expr> is evaluated.

The expression `declare(<x>, evflag)` gives the `evflag` property to the variable <x>.

The flags which have the `evflag` property by default are the following: `algebraic`, `cauchysum`, `demoivre`, `dotscrules`, `%emode`, `%enumer`, `exponentialize`, `exptisolate`, `factorflag`, `float`, `halfangles`, `infeval`, `isolate_wrt_times`, `keepfloat`, `letrat`, `listarith`, `logabs`, `logarc`, `logexpand`, `lognegint`, `lognumer`, `m1pbranch`, `numer_pbranch`, `programmode`, `radexpand`, `ratalgdenom`, `ratfac`, `ratmx`, `ratsimpexpons`, `simp`, `simpproduct`, `simpsum`, `sumexpand`, and `trigexpand`.

Examples:

```          (%i1) sin (1/2);
1
(%o1)                        sin(-)
2
(%i2) sin (1/2), float;
(%o2)                   0.479425538604203
(%i3) sin (1/2), float=true;
(%o3)                   0.479425538604203
(%i4) simp : false;
(%o4)                         false
(%i5) 1 + 1;
(%o5)                         1 + 1
(%i6) 1 + 1, simp;
(%o6)                           2
(%i7) simp : true;
(%o7)                         true
(%i8) sum (1/k^2, k, 1, inf);
inf
====
\     1
(%o8)                        >    --
/      2
====  k
k = 1
(%i9) sum (1/k^2, k, 1, inf), simpsum;
2
%pi
(%o9)                         ----
6
(%i10) declare (aa, evflag);
(%o10)                        done
(%i11) if aa = true then YES else NO;
(%o11)                         NO
(%i12) if aa = true then YES else NO, aa;
(%o12)                         YES```

```(%o1)                                true
(%i2) ```

? evflag;

Calculate

evflag(%sqrt7);

Calculate

evflag(sqrt7);

Calculate

? evflag;

Calculate

evflag(%sqrt7);

Calculate

evflag(sqrt7);

Calculate