Option variable
assume_pos_pred
Default value: false
When assume_pos_pred
is assigned the name of a function
or a lambda expression of one argument x,
that function is called to determine
whether x is considered a parameter for the purpose of assume_pos
.
assume_pos_pred
is ignored when assume_pos
is false
.
The assume_pos_pred
function is called by sign
and asksign
with an argument x
which is either an atom, a subscripted variable, or a function call expression.
If the assume_pos_pred
function returns true
,
x is considered a parameter for the purpose of assume_pos
.
By default, a parameter is x such that symbolp (x)
or subvarp (x)
.
Examples:
(%i1) assume_pos: true$ (%i2) assume_pos_pred: symbolp$ (%i3) sign (a); (%o3) pos (%i4) sign (a[1]); (%o4) pnz (%i5) assume_pos_pred: lambda ([x], display (x), true)$ (%i6) asksign (a); x = a (%o6) pos (%i7) asksign (a[1]); x = a 1 (%o7) pos (%i8) asksign (foo (a)); x = foo(a) (%o8) pos (%i9) asksign (foo (a) + bar (b)); x = foo(a) x = bar(b) (%o9) pos (%i10) asksign (log (a)); x = a Is a - 1 positive, negative, or zero? p; (%o10) pos (%i11) asksign (a - b); x = a x = b x = a x = b Is b - a positive, negative, or zero? p; (%o11) neg