add cmd/dataunit, example

examples/parse_units.v

@@ -0,0 +1,36 @@
+import os
+import regex
+import dataunits
+
+struct Memory {
+	value f64
+	unit  dataunits.DataSize
+}
+
+fn (m Memory) str() string {
+	return '${m.value} ${dataunits.to_string(m.unit) or { '' }}'
+}
+
+fn (m Memory) mib() f64 {
+	return dataunits.convert(m.value, m.unit, dataunits.mib)
+}
+
+fn Memory.from_string(s string) !Memory {
+	mut re := regex.regex_opt(r'^(\d+)([a-zA-Z]+)$')!
+	re.match_string(s)
+	if re.groups.len < 2 {
+		return error('unable to parse string ${s}')
+	}
+	value := re.get_group_by_id(s, 0).f64()
+	unit := dataunits.from_string(re.get_group_by_id(s, 1))!
+	return Memory{value, unit}
+}
+
+fn main() {
+	mem := Memory.from_string(os.input('Enter memory value (e.g. 10Gi): ')) or {
+		eprintln('Error: ${err}')
+		exit(1)
+	}
+	println('Input: ${mem}')
+	println('Memory size: ${mem.mib()} MiB')
+}