swab(1): fix some silly mistakes

src/swab.rs

@@ -24,7 +24,7 @@ use std::{
 };
 
 extern crate getopt;
-use getopt::{ Opt, Parser };
+use getopt::GetOpt;
 
 extern crate sysexits;
 use sysexits::{ EX_OK, EX_OSERR, EX_USAGE };
@@ -45,7 +45,6 @@ fn main() -> ExitCode {
 	let mut input = stdin();
 	let mut output = stdout().lock();
 
-	let mut opts = Parser::new(&argv, "fw:");
 	let mut force = false;
 	let mut wordsize: usize = 2;
 
@@ -53,10 +52,12 @@ fn main() -> ExitCode {
 		match opt.opt() {
 			Ok("f") => force = true,
 			Ok("w") => {
-					match arg.parse::<usize>() {
+				if let Some(arg) = opt.arg() {
+					match opt.arg().parse::<usize>() {
 						Ok(w) if w % 2 == 0 => { wordsize = w; () },
 						_ => { return usage(&argv[0]); },
 					}
+				}
 			},
 			_ => { return usage(&argv[0]); }
 		}