Work on conversion of args parsing to go code

tools/cmd/at/scroll_window.go

@@ -0,0 +1,40 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package at
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func parse_scroll_amount(amt string) ([2]interface{}, error) {
+	var ans [2]interface{}
+	if amt == "start" || amt == "end" {
+		ans[0] = amt
+		ans[1] = nil
+	} else {
+		pages := strings.Contains(amt, "p")
+		unscroll := strings.Contains(amt, "u")
+		var mult float64 = 1
+		if strings.HasSuffix(amt, "-") && !unscroll {
+			mult = -1
+			q, err := strconv.ParseFloat(strings.TrimRight(amt, "+-plu"), 64)
+			if err != nil {
+				return ans, err
+			}
+			if !pages && q != float64(int(q)) {
+				return ans, fmt.Errorf("The number must be an integer")
+			}
+			ans[0] = q * mult
+			if pages {
+				ans[1] = "p"
+			} else if unscroll {
+				ans[1] = "u"
+			} else {
+				ans[1] = "l"
+			}
+		}
+	}
+	return ans, nil
+}