parser: add support for unary operators

7 files changed, 46 insertions, 4 deletions

diff --git a/lang/golang/go.go b/lang/golang/go.go
index 26af4f3..f5a6578 100644
--- a/lang/golang/go.go
+++ b/lang/golang/go.go
@@ -91,6 +91,7 @@ var GoSpec = &lang.Spec{
 		"<=": {TokenId: lang.LessEqual, Precedence: 3},
 		">=": {TokenId: lang.GreaterEqual, Precedence: 3},
 		"->": {TokenId: lang.Arrow},
+		"!":  {TokenId: lang.Not},
 		"++": {TokenId: lang.Inc, SkipSemi: true},
 		"--": {TokenId: lang.Dec, SkipSemi: true},
 
diff --git a/lang/token.go b/lang/token.go
index a894c98..4bf9bf2 100644
--- a/lang/token.go
+++ b/lang/token.go
@@ -116,6 +116,16 @@ const (
 	EqualSet
 )
 
+var UnaryOp = map[TokenId]TokenId{
+	Add:   Plus,    // +
+	And:   Address, // &
+	Not:   Not,     // !
+	Mul:   Deref,   // *
+	Sub:   Minus,   // -
+	Tilde: Tilde,   // ~
+	Xor:   BitComp, // ^
+}
+
 func (t TokenId) IsKeyword() bool   { return t >= Break && t <= Var }
 func (t TokenId) IsLiteral() bool   { return t >= Char && t <= String }
 func (t TokenId) IsOperator() bool  { return t >= Add && t <= Tilde }
diff --git a/parser/README.md b/parser/README.md
index eb65dcf..118d9aa 100644
--- a/parser/README.md
+++ b/parser/README.md
@@ -34,7 +34,7 @@ Go language support:
 - [ ] export to runtime
 - [ ] builtin calls (new, make, copy, delete, len, cap, ...)
 - [ ] out of order declarations
-- [ ] arbirtrary precision constants
+- [x] arbirtrary precision constants
 - [x] basic types
 - [ ] complete numeric types
 - [x] function types
@@ -43,6 +43,7 @@ Go language support:
 - [x] structures
 - [ ] embedded structures
 - [ ] recursive structures
+- [ ] literal composite objects
 - [ ] interfaces
 - [x] arrays, slices
 - [ ] maps
@@ -70,7 +71,7 @@ Go language support:
 - [x] label statement
 - [ ] select statement
 - [x] binary operators
-- [ ] unary operators
+- [x] unary operators
 - [x] logical operators && and ||
 - [ ] assign operators
 - [x] operator precedence rules
@@ -78,6 +79,7 @@ Go language support:
 - [x] call expressions
 - [x] index expressions
 - [x] selector expressions
+- [ ] slice expressions
 - [ ] type convertions
 - [ ] type assertions
 - [ ] parametric types (generic)
diff --git a/parser/compiler.go b/parser/compiler.go
index 41448b7..bdf801b 100644
--- a/parser/compiler.go
+++ b/parser/compiler.go
@@ -77,6 +77,16 @@ func (c *Compiler) Codegen(tokens Tokens) (err error) {
 			push(&symbol{Type: arithmeticOpType(pop(), pop())})
 			emit(int64(t.Pos), vm.Sub)
 
+		case lang.Minus:
+			emit(int64(t.Pos), vm.Push, 0)
+			emit(int64(t.Pos), vm.Sub)
+
+		case lang.Not:
+			emit(int64(t.Pos), vm.Not)
+
+		case lang.Plus:
+			// Nothing to do.
+
 		case lang.Index:
 			emit(int64(t.Pos), vm.Index)
 
diff --git a/parser/expr.go b/parser/expr.go
index fa8afa4..207f38b 100644
--- a/parser/expr.go
+++ b/parser/expr.go
@@ -42,10 +42,21 @@ func (p *Parser) ParseExpr(in Tokens) (out Tokens, err error) {
 		case lang.Int, lang.String:
 			out = append(out, t)
 			vl++
-		case lang.Define, lang.Add, lang.Sub, lang.Assign, lang.Equal, lang.Greater, lang.Less, lang.Mul, lang.Land, lang.Lor, lang.Shl, lang.Shr:
+		case lang.Define, lang.Add, lang.Sub, lang.Assign, lang.Equal, lang.Greater, lang.Less, lang.Mul, lang.Land, lang.Lor, lang.Shl, lang.Shr, lang.Not:
+			if i == 0 || in[i-1].Id.IsOperator() {
+				// An operator preceded by an operator or no token is unary.
+				t.Id = lang.UnaryOp[t.Id]
+				j := len(out) - 1
+				l := out[j]
+				if p.precedence(l) > 0 {
+					out = append(out[:j], t, l)
+					break
+				}
+				out = append(out, t)
+				break
+			}
 			if vl < 2 {
 				ops = append(ops, t)
-				break
 			}
 		case lang.ParenBlock:
 			// If the previous token is an arithmetic, logic or assign operator then
diff --git a/parser/interpreter_test.go b/parser/interpreter_test.go
index 308474c..db9b916 100644
--- a/parser/interpreter_test.go
+++ b/parser/interpreter_test.go
@@ -65,6 +65,10 @@ func TestExpr(t *testing.T) {
 		{src: "7 == 2 * 3 + 1", res: "true"},
 		{src: "1 + 3 * 2 == 2 * 3 + 1", res: "true"},
 		{src: "a := 1 + 3 * 2 == 2 * 3 + 1; a", res: "true"},
+		{src: "-2", res: "-2"},
+		{src: "-2 + 5", res: "3"},
+		{src: "5 + -2", res: "3"},
+		{src: "!false", res: "true"},
 	})
 }
 
diff --git a/vm/vm.go b/vm/vm.go
index fa31ff0..21205de 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -37,6 +37,7 @@ const (
 	Lower               // n1 n2 -- cond ; cond = n1 < n2
 	Loweri              // n1 -- cond ; cond = n1 < $1
 	Mul                 // n1 n2 -- prod ; prod = n1*n2
+	Not                 // c -- r ; r = !c
 	Pop                 // v --
 	Push                // -- v
 	Return              // [r1 .. ri] -- ; exit frame: sp = fp, fp = pop
@@ -69,6 +70,7 @@ var strop = [...]string{ // for VM tracing.
 	Lower:        "Lower",
 	Loweri:       "Loweri",
 	Mul:          "Mul",
+	Not:          "Not",
 	Pop:          "Pop",
 	Push:         "Push",
 	Return:       "Return",
@@ -210,6 +212,8 @@ func (m *Machine) Run() (err error) {
 			mem = mem[:sp-1]
 		case Loweri:
 			mem[sp-1] = mem[sp-1].(int) < int(op[2])
+		case Not:
+			mem[sp-1] = !mem[sp-1].(bool)
 		case Pop:
 			mem = mem[:sp-int(op[2])]
 		case Push: