fix: correct and simplify parsing of expressions.

The expressions were parsed from right to left, and it was incorrect and
cumbersome. Now they are processed from left to right, with a simpler
and correct handling of precedence rules.

The vm function call syntax has been changed to set the function
before the input arguments on the stack, as to follow the declaring
order in languages.

1 files changed, 21 insertions, 13 deletions

diff --git a/vm/vm.go b/vm/vm.go
index 6472156..caf9189 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -24,7 +24,7 @@ const (
 	Addr                   // a -- &a ;
 	Assign                 // val -- ; mem[$1] = val
 	Fassign                // val -- ; mem[$1] = val
-	Vassign                // val dest -- ; dest.Set(val)
+	Vassign                // dest val -- ; dest.Set(val)
 	Call                   // f [a1 .. ai] -- [r1 .. rj] ; r1, ... = prog[f](a1, ...)
 	Calli                  // f [a1 .. ai] -- [r1 .. rj] ; r1, ... = prog[f](a1, ...)
 	CallX                  // f [a1 .. ai] -- [r1 .. rj] ; r1, ... = mem[f](a1, ...)
@@ -49,6 +49,7 @@ const (
 	Loweri                 // n1 -- cond ; cond = n1 < $1
 	Mul                    // n1 n2 -- prod ; prod = n1*n2
 	New                    // -- x; mem[fp+$1] = new mem[$2]
+	Negate                 // -- ; - mem[fp]
 	Not                    // c -- r ; r = !c
 	Pop                    // v --
 	Push                   // -- v
@@ -119,10 +120,13 @@ func (m *Machine) Run() (err error) {
 			mem[fp+c.Arg[0]-1].Set(mem[sp-1].Value)
 			mem = mem[:sp-1]
 		case Call:
-			nip := int(mem[sp-1].Int())
-			mem = append(mem[:sp-1], ValueOf(ip+1), ValueOf(fp))
+			// nip := int(mem[sp-1].Int())
+			// mem = append(mem[:sp-1], ValueOf(ip+1), ValueOf(fp))
+			nip := int(mem[sp-1-c.Arg[0]].Int())
+			mem = append(mem, ValueOf(ip+1), ValueOf(fp))
 			ip = nip
-			fp = sp + 1
+			// fp = sp + 1
+			fp = sp + 2
 			continue
 		case Calli:
 			mem = append(mem, ValueOf(ip+1), ValueOf(fp))
@@ -132,9 +136,9 @@ func (m *Machine) Run() (err error) {
 		case CallX: // Should be made optional.
 			in := make([]reflect.Value, c.Arg[0])
 			for i := range in {
-				in[i] = mem[sp-2-i].Value
+				in[i] = mem[sp-1-i].Value
 			}
-			f := mem[sp-1].Value
+			f := mem[sp-1-c.Arg[0]].Value
 			mem = mem[:sp-c.Arg[0]-1]
 			for _, v := range f.Call(in) {
 				mem = append(mem, Value{Value: v})
@@ -142,7 +146,8 @@ func (m *Machine) Run() (err error) {
 		case Deref:
 			mem[sp-1].Value = mem[sp-1].Value.Elem()
 		case Dup:
-			mem = append(mem, mem[c.Arg[0]])
+			k := c.Arg[0]
+			mem = append(mem, mem[k])
 		case New:
 			mem[c.Arg[0]+fp-1] = NewValue(mem[c.Arg[1]].Type)
 		case Equal:
@@ -214,13 +219,15 @@ func (m *Machine) Run() (err error) {
 			}
 			mem = mem[:sp-1]
 		case Greater:
-			mem[sp-2] = ValueOf(mem[sp-1].Int() > mem[sp-2].Int())
+			mem[sp-2] = ValueOf(mem[sp-2].Int() > mem[sp-1].Int())
 			mem = mem[:sp-1]
 		case Lower:
-			mem[sp-2] = ValueOf(mem[sp-1].Int() < mem[sp-2].Int())
+			mem[sp-2] = ValueOf(mem[sp-2].Int() < mem[sp-1].Int())
 			mem = mem[:sp-1]
 		case Loweri:
 			mem[sp-1] = ValueOf(mem[sp-1].Int() < int64(c.Arg[0]))
+		case Negate:
+			mem[sp-1] = ValueOf(-mem[sp-1].Int())
 		case Not:
 			mem[sp-1] = ValueOf(!mem[sp-1].Bool())
 		case Pop:
@@ -234,10 +241,10 @@ func (m *Machine) Run() (err error) {
 			ip = int(mem[fp-2].Int())
 			ofp := fp
 			fp = int(mem[fp-1].Int())
-			mem = append(mem[:ofp-c.Arg[0]-c.Arg[1]-1], mem[sp-c.Arg[0]:]...)
+			mem = append(mem[:ofp-c.Arg[0]-c.Arg[1]-2], mem[sp-c.Arg[0]:]...)
 			continue
 		case Sub:
-			mem[sp-2] = ValueOf(int(mem[sp-1].Int() - mem[sp-2].Int()))
+			mem[sp-2] = ValueOf(int(mem[sp-2].Int() - mem[sp-1].Int()))
 			mem = mem[:sp-1]
 		case Subi:
 			mem[sp-1] = ValueOf(int(mem[sp-1].Int()) - c.Arg[0])
@@ -245,10 +252,11 @@ func (m *Machine) Run() (err error) {
 			a, b := sp-c.Arg[0]-1, sp-c.Arg[1]-1
 			mem[a], mem[b] = mem[b], mem[a]
 		case Index:
-			mem[sp-2].Value = mem[sp-1].Index(int(mem[sp-2].Int()))
+			mem[sp-2].Value = mem[sp-2].Index(int(mem[sp-1].Int()))
 			mem = mem[:sp-1]
 		case Vassign:
-			mem[sp-1].Set(mem[sp-2].Value)
+			// mem[sp-1].Set(mem[sp-2].Value)
+			mem[sp-2].Set(mem[sp-1].Value)
 			mem = mem[:sp-2]
 		}
 		ip++