fix unary parsing

TODO.md

@@ -3,4 +3,7 @@
 * Conversion methods
   * `v.format()`
   * `v.parse_int()`
-  * `v.parse_float()`
+  * `v.parse_float()`
+* Note about iterator efficiency [here](https://github.com/facebook/rocksdb/wiki/Reducing-memcpy-overhead-when-using-Iterators)
+* Homogeneous array types
+  * Alignment could imply necessary copies (COW)

src/grammar.pest

@@ -83,7 +83,7 @@ literal = _{ null | boolean | number | string}
 // expressions
 
 comma_sep_expr = { expr ~ ("," ~ expr)* }
-expr = {(unary | term) ~ (operation ~ (unary | term)) *}
+expr = {unary ~ (operation ~ unary) *}
 operation = _{ (op_and | op_or | op_pow | op_str_cat | op_add | op_sub | op_mul | op_div | op_mod | op_coalesce |
                 op_ge | op_le | op_gt | op_lt | op_eq | op_ne)}
 op_or = { "||" }
@@ -103,7 +103,7 @@ op_ge = { ">=" }
 op_le = { "<=" }
 op_pow = { "^" }
 
-unary = { unary_op ~ term }
+unary = { (unary_op ~ unary) | term }
 unary_op = _{ minus | negate }
 minus = { "-" }
 negate = { "!" }

src/relation/value.rs

@@ -107,7 +107,7 @@ pub enum Value<'a> {
     // not evaluated
     Variable(Cow<'a, str>),
     TupleRef(TableId, ColId),
-    Apply(Cow<'a, str>, Vec<Value<'a>>),
+    Apply(Cow<'a, str>, Vec<Value<'a>>),  // TODO optimization: special case for small number of args (esp. 0, 1, 2)
     FieldAccess(Cow<'a, str>, Box<Value<'a>>),
     IdxAccess(usize, Box<Value<'a>>),
     // cannot exist
@@ -486,13 +486,15 @@ fn build_expr_primary(pair: Pair<Rule>) -> Result<Value> {
 
         Rule::unary => {
             let mut inner = pair.into_inner();
-            let op = inner.next().unwrap().as_rule();
-            let term = build_expr_primary(inner.next().unwrap())?;
+            let p = inner.next().unwrap();
+            let op = p.as_rule();
             let op = match op {
+                Rule::term => return build_expr_primary(p),
                 Rule::negate => OP_NEGATE,
                 Rule::minus => OP_MINUS,
                 _ => unreachable!()
             };
+            let term = build_expr_primary(inner.next().unwrap())?;
             Ok(Value::Apply(op.into(), vec![term]))
         }