How would I find the sum of an argument, with the constraint that they are all integers (so if the argument contains a non-integer value, the function will not evaluate).
I came up with these two:
sumInts[n__?(IntegerQ[#] &)] := +n
sum[x__Integer] := +x
Both are impure functions (though the first function uses a pure predicate). How would I go about making a pure function? I couldn't figure out how to because of the Integer constraint.