ReqNum.pos constructor
Constrains data to positive numbers (zero included).
blank
the error message in case of a null or empty input value.
mal
"malformed", the error message in case of non-numeric input values.
neg
the error message if an input value is negative.
Implementation
ReqNum.pos({String? blank, String? mal, String? neg})
: this._num(Num.pos(mal: mal, neg: neg), blank);