bool valid$\_$identifier$($const strings str$)$; identifier contains only letters, digits, and underscores and may not start with a digit.

For example, the following function calls shall return true:

valid$\_$identifier$("$ab$\_$cb$\_$l$")($Valid$\_$identifier$("$abCD$1")$

valid$\_$identifier ${(}_{-}{)}^{.}.$ valid$\_$identifier $("$a$")$

valid$\_$identifier ${(}^{-}{1}^n).$ valid$\_$identifier$("$C$\_")$

The following function calls shall return false:

valid identifier $(ab-CD-1).$ valid identifier$("$ab CD $1")$

valid$\_$identifier $(l{a}^{\text{'}}).$ valid$\_$identifier$("$a$$")$

$($Hint: Declare a bool variable and set it to true. Then set up a loop to iterate through the characters and break out of the loop when an invalid character is present.$)$

The following illustrates a sample output of incomplete testing. The first column shows the identifiers being tested and the second column shows the result of the valid identifier function.

IDENTIFIERVALID OR NOT

$\backslash$table$[[a{b}_c{D}_{-1},$true$],[$abcot$,$true$],[$ab$-$cd$-1,$false$],[,$true$]]$