add "swap" instr, document buffer ops

crsn_buf/src/parse.rs

@@ -12,40 +12,32 @@ pub(crate) fn parse<'a>(_pos: &SourcePosition, keyword: &str, mut args: TokenPar
     Ok(ParseRes::ext(match keyword {
         "mkbf" => {
             let dst = args.next_wr()?;
-            let len = if args.have_more() {
-                args.next_rd()?
-            } else {
-                Rd::immediate(0)
-            };
-            BufOps::New { dst, value: BufValue::Zeros(len) }
-        }
 
-        "mkbfv" => {
-            let dst = args.next_wr()?;
-
-            let next = args.next_or_err()?;
-
-            match next {
-                Sexp::Atom(Atom::QS(s), _) => {
-                    BufOps::New {
-                        dst,
-                        value: BufValue::Chars(s),
-                    }
+            let value = match args.next() {
+                None => {
+                    BufValue::Zeros(Rd::immediate(0))
                 }
-                Sexp::List(list, _) => {
+                Some(tok @ Sexp::Atom(Atom::S(_), _)) |
+                Some(tok @ Sexp::Atom(Atom::I(_), _)) |
+                Some(tok @ Sexp::Atom(Atom::U(_), _)) => {
+                    BufValue::Zeros(parse_rd(tok, args.pcx)?)
+                }
+                Some(Sexp::Atom(Atom::QS(s), _)) => {
+                    BufValue::Chars(s)
+                }
+                Some(Sexp::List(list, _)) => {
                     let mut vals = vec![];
                     for v in list {
                         vals.push(parse_rd(v, args.pcx)?);
                     }
-                    BufOps::New {
-                        dst,
-                        value: BufValue::Values(vals),
-                    }
+                    BufValue::Values(vals)
                 }
-                other => {
+                Some(other) => {
                     return Err(CrsnError::Parse("Expected quoted string or a tuple of values".into(), other.pos().clone()));
                 }
-            }
+            };
+
+            BufOps::New { dst, value }
         }
 
         "bfrd" => {