diff --git a/day4/part2/main.d b/day4/part2/main.d
index b897b69..b4b8196 100644
--- a/day4/part2/main.d
+++ b/day4/part2/main.d
@@ -17,31 +17,6 @@ auto parsePassports(string input)
         }).assocArray);
 }
 
-enum Field : string
-{
-    birthYear = "byr",
-    issueYear = "iyr",
-    expirationYear = "eyr",
-    height = "hgt",
-    hairColor = "hcl",
-    eyeColor = "ecl",
-    passportID = "pid",
-    countryID = "cid",
-}
-
-bool isValidYear(int min, int max)(string yr)
-{
-    if (yr.length != 4 || yr.canFind!(not!isDigit))
-        return false;
-    auto year = yr.to!int;
-    return year >= min && year <= max;
-
-}
-
-alias isValidBirthYear = isValidYear!(1920, 2002);
-alias isValidIssueYear = isValidYear!(2010, 2020);
-alias isValidExpirationYear = isValidYear!(2020, 2030);
-
 bool isValidHeight(string hgt)
 {
     auto match = hgt.matchFirst(r"^(\d+)(cm|in)$");
@@ -61,36 +36,24 @@ bool isValidHeight(string hgt)
     }
 }
 
-bool isValidHairColor(string hcl)
-{
-    return hcl.matchFirst(r"^#[0-9a-f]{6}$").to!bool;
-}
-
-bool isValidEyeColor(string ecl)
-{
-    return ["amb", "blu", "brn", "gry", "grn", "hzl", "oth"].canFind(ecl);
-}
-
-bool isValidPassportID(string pid)
-{
-    return pid.matchFirst(r"^\d{9}$").to!bool;
-}
-
-enum requiredFields = [
-        Field.birthYear, Field.issueYear, Field.expirationYear, Field.height,
-        Field.hairColor, Field.eyeColor, Field.passportID
-    ];
+alias isBetween = (x, min, max) => x >= min && x <= max;
 
 bool isValidPassport(Passport passport)
 {
-    return requiredFields.all!(field => field in passport)
-        && isValidBirthYear(passport[Field.birthYear])
-        && isValidIssueYear(passport[Field.issueYear])
-        && isValidExpirationYear(passport[Field.expirationYear])
-        && isValidHeight(passport[Field.height])
-        && isValidHairColor(passport[Field.hairColor])
-        && isValidEyeColor(passport[Field.eyeColor])
-        && isValidPassportID(passport[Field.passportID]);
+    // dfmt off
+    auto validators = [
+        "byr" : s => s.length == 4 && s.all!isDigit && s.to!int.isBetween(1920, 2002),
+        "iyr" : s => s.length == 4 && s.all!isDigit && s.to!int.isBetween(2010, 2020),
+        "eyr" : s => s.length == 4 && s.all!isDigit && s.to!int.isBetween(2020, 2030),
+        "hgt" : &isValidHeight,
+        "hcl" : s => s.matchFirst(r"^#[0-9a-f]{6}$").to!bool,
+        "ecl" : s => [ "amb", "blu", "brn", "gry", "grn", "hzl", "oth" ].canFind(s),
+        "pid" : s => s.matchFirst(r"^\d{9}$").to!bool
+    ];
+    // dfmt on
+
+    return validators.byKeyValue.all!(validator => validator.key in passport
+            && validator.value()(passport[validator.key]));
 }
 
 auto countValidPassports(R)(R r) if (isInputRange!R && is(ElementType!R == Passport))