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
,
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