 invalid power - Maple Help

Error, invalid power

Error, non-algebraic exponent Description

This error occurs when you attempt to raise an expression to an invalid power, such as a string.  See example 1.

Reserved symbols that cannot represent a numerical value are invalid powers. By default, Maple assumes that an invalid power implies that the entire expression, for example, ${x}^{#}$  is to be taken atomically as an expression unto itself (an expression that cannot be broken down into its component meanings).

 > $\mathrm{restart}$
 > ${x}^{#}$
 ${{x}}^{{#}}$ (1.1)

This error can also occur when you have attempted to raise an expression to an invalid power while Typesetting:-Settings(autoatomic=false).  See example 2.

Tip: If an expression is executed accidentally, it can lead to error messages (if it is not valid Maple syntax). If this happens, toggling the expression to nonexecutable math removes the error message and changes the math to nonexecutable. To change an expression to nonexecutable math use the shortcut key Shift + F5.  For more information, see Executable and Nonexecutable Math. Examples

Example 1:

A string is not a valid exponent.

 > ${x}^{"two"}$
 

With 1-D math input, the error message is different.

 > ${x}^{"two"}$

Solution: Use a valid expression for the exponent, such as a name or numerical value.

 >
 ${{x}}^{{a}}$
 ${{x}}^{{2}}$ (2.1)

Example 2:

The following value is identified as an atomic object.

 > $\mathrm{restart}$
 > ${x}^{@}$
 ${{x}}^{{@}}$ (2.2)

The same value produces an error because autoatomic is set to false.

 > $\mathrm{restart}$
 > $\mathrm{Typesetting}\left[\mathrm{Settings}\right]\left(\mathrm{autoatomic}=\mathrm{false}\right):$
 > ${x}^{@}$
 

Solution: This automatic behavior can be disabled by setting the Typesetting[Settings] command to true, or via the Typesetting Rule Assistant.

 > $\mathrm{Typesetting}\left[\mathrm{Settings}\right]\left(\mathrm{autoatomic}=\mathrm{true}\right):$
 > ${x}^{@}$
 ${{x}}^{{@}}$ (2.3)