move: advanced funcs to functional programming

27-functional-programming/log-parser-exp/field.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// field helps for field parsing
+type field struct{ err error }
+
+// uatoi parses an unsigned integer string and saves the error.
+// it assumes that the val is unsigned.
+// for ease of usability: it returns an int instead of uint.
+func (f *field) uatoi(name, val string) int {
+	n, err := strconv.Atoi(val)
+	if n < 0 || err != nil {
+		f.err = fmt.Errorf("incorrect field -> %q = %q", name, val)
+	}
+	return n
+}