**Error:**
(in limit) invalid directional argument

The
**limit**
command has an optional third argument, which allows the calculation of various types of limits, e.g. one-sided limits. The allowed values for this argument are
**left**
,
**right**
,
**real**
and
**complex**
. Anything else produces this error message.

One way this error sometimes arises is that someone uses
**left**
or
**right**
as a variable and assigns it a value. It seems to work at first: these are not protected names. But when you try to evaluate a definite integral, this error appears. The reason is that Maple's code for definite integrals calls
**limit**
with the options
**left**
and
**right**
to evaluate the antiderivative at the endpoints of its interval. If
**left**
or
**right**
has been assigned a value, this will not work.

**Examples:**

`> `
**limit(2^(1/x), x=0, left);**

`> `
**limit(2^(1/x), x=0, LEFT);**

Error, (in limit) invalid directional argument

Assigning a value to
**left**
causes errors:

`> `
**left:= 4:**

`> `
**limit(2^(1/x), x=0, left);**

Error, (in limit) invalid directional argument

`> `
**int(x, x=0 .. 2);**

Error, (in limit) invalid directional argument

Unassigning
**left**
fixes the problem.

`> `
**left:= 'left':**

`> `
**int(x, x=0 .. 2);**

**See also:**
__limit__
,
__int__

**Maple Advisor Database**
R. Israel, 1997