Why does Stata return “unknown function +inrange()”?

I am studying Stata programming with the book An Introduction to Stata Programming, Second Edition.

In chapter 4 there is code to generate a variable that tests whether some other variables satisfy a logical condition, the code is like:

foreach v of varlist child1-child12{
        local n_school "`n_school' + inrange(`v', 1, 5)"
    }
    gen n_school = `n_school'

When I change this code to suit my own data,

foreach v of varlist qp605_s_1-qp605_s_5 {
        local n_med  "`n_med' + inrange(`v', 1, 5)"
    }
    gen n_med = `n_med'

where qp605_s_1's values range from 1 to 17, then Stata returns:

. foreach v of varlist qp605_s_1-qp605_s_5 {
  2.         local n_med "`n_med' + inrange(`v', 1, 5)"
  3. }

. gen n_med = `n_med'
unknown function +inrange()
r(133);

Any ideas what is wrong with this code?

Here is another approach.

* Example generated by -dataex-. For more info, type help dataex
clear
input float(var1 var2)
1 5
2 6
3 7
4 8
end

gen wanted = .

mata :

data = st_data(., "var*")

st_store(., "wanted", rowsum(data :>= 1 :& data :<= 5))

end

list

     +----------------------+
     | var1   var2   wanted |
     |----------------------|
  1. |    1      5        2 |
  2. |    2      6        1 |
  3. |    3      7        1 |
  4. |    4      8        1 |
     +----------------------+