Method on @sym: isfinite (x) ¶

Is symbolic expression finite.

A number is finite if it is neither infinite (see ‘@sym/isinf’) nor NaN (see ‘@sym/isnan’), for example:

isfinite (sym(42))
  ⇒ ans =  1
isfinite (sym(inf))
  ⇒ ans =  0
isfinite (sym(nan))
  ⇒ ans =  0

However for symbolic expressions, the situation is more complicated, for example we cannot be sure x is finite:

syms x
isfinite (x)
  ⇒ ans =  0

Of course, we also cannot be sure x is infinite:

isinf (x)
  ⇒ ans =  0

Assumptions play a role:

syms x finite
isfinite (x)
  ⇒ ans =  1

isfinite (1/x)            % x could be zero
  ⇒ ans =  0

syms y positive finite
isfinite (1/y)
  ⇒ ans =  1

See also: @sym/isinf, @sym/isnan.

Package: symbolic