Add support for unary operators + and - to the interpolation syntax

config/lang/ast/unary_arithmetic.go

@@ -0,0 +1,42 @@
+package ast
+
+import (
+	"fmt"
+)
+
+// UnaryArithmetic represents a node where the result is arithmetic of
+// one operands
+type UnaryArithmetic struct {
+	Op   ArithmeticOp
+	Expr Node
+	Posx Pos
+}
+
+func (n *UnaryArithmetic) Accept(v Visitor) Node {
+	n.Expr = n.Expr.Accept(v)
+
+	return v(n)
+}
+
+func (n *UnaryArithmetic) Pos() Pos {
+	return n.Posx
+}
+
+func (n *UnaryArithmetic) GoString() string {
+	return fmt.Sprintf("*%#v", *n)
+}
+
+func (n *UnaryArithmetic) String() string {
+	var sign rune
+	switch n.Op {
+	case ArithmeticOpAdd:
+		sign = '+'
+	case ArithmeticOpSub:
+		sign = '-'
+	}
+	return fmt.Sprintf("%c%s", sign, n.Expr)
+}
+
+func (n *UnaryArithmetic) Type(Scope) (Type, error) {
+	return TypeInt, nil
+}

config/lang/builtins.go

@@ -24,11 +24,53 @@ func registerBuiltins(scope *ast.BasicScope) *ast.BasicScope {
 	scope.FuncMap["__builtin_StringToInt"] = builtinStringToInt()
 
 	// Math operations
+	scope.FuncMap["__builtin_UnaryIntMath"] = builtinUnaryIntMath()
+	scope.FuncMap["__builtin_UnaryFloatMath"] = builtinUnaryFloatMath()
 	scope.FuncMap["__builtin_IntMath"] = builtinIntMath()
 	scope.FuncMap["__builtin_FloatMath"] = builtinFloatMath()
 	return scope
 }
 
+func builtinUnaryIntMath() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeInt},
+		Variadic:   false,
+		ReturnType: ast.TypeInt,
+		Callback: func(args []interface{}) (interface{}, error) {
+			op := args[0].(ast.ArithmeticOp)
+			result := args[1].(int)
+			switch op {
+			case ast.ArithmeticOpAdd:
+				result = result
+			case ast.ArithmeticOpSub:
+				result = -result
+			}
+
+			return result, nil
+		},
+	}
+}
+
+func builtinUnaryFloatMath() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeFloat},
+		Variadic:   false,
+		ReturnType: ast.TypeFloat,
+		Callback: func(args []interface{}) (interface{}, error) {
+			op := args[0].(ast.ArithmeticOp)
+			result := args[1].(float64)
+			switch op {
+			case ast.ArithmeticOpAdd:
+				result = result
+			case ast.ArithmeticOpSub:
+				result = -result
+			}
+
+			return result, nil
+		},
+	}
+}
+
 func builtinFloatMath() ast.Function {
 	return ast.Function{
 		ArgTypes:     []ast.Type{ast.TypeInt},

config/lang/check_types.go

@@ -55,6 +55,9 @@ func (v *TypeCheck) visit(raw ast.Node) ast.Node {
 	var result ast.Node
 	var err error
 	switch n := raw.(type) {
+	case *ast.UnaryArithmetic:
+		tc := &typeCheckUnaryArithmetic{n}
+		result, err = tc.TypeCheck(v)
 	case *ast.Arithmetic:
 		tc := &typeCheckArithmetic{n}
 		result, err = tc.TypeCheck(v)
@@ -89,6 +92,48 @@ func (v *TypeCheck) visit(raw ast.Node) ast.Node {
 	return result
 }
 
+type typeCheckUnaryArithmetic struct {
+	n *ast.UnaryArithmetic
+}
+
+func (tc *typeCheckUnaryArithmetic) TypeCheck(v *TypeCheck) (ast.Node, error) {
+	// Only support + or - as unary op
+	if tc.n.Op != ast.ArithmeticOpAdd && tc.n.Op != ast.ArithmeticOpSub {
+		fmt.Printf("%+v\n", tc.n.Op)
+		return nil, fmt.Errorf("only + or - supported as unary operator")
+	}
+	expr := v.StackPop()
+
+	mathFunc := "__builtin_UnaryIntMath"
+	mathType := ast.TypeInt
+	switch expr {
+	case ast.TypeInt:
+		mathFunc = "__builtin_UnaryIntMath"
+		mathType = expr
+	case ast.TypeFloat:
+		mathFunc = "__builtin_UnaryFloatMath"
+		mathType = expr
+	}
+
+	// Return type
+	v.StackPush(mathType)
+
+	args := make([]ast.Node, 2)
+	args[0] = &ast.LiteralNode{
+		Value: tc.n.Op,
+		Typex: ast.TypeInt,
+		Posx:  tc.n.Pos(),
+	}
+	args[1] = tc.n.Expr
+	// Replace our node with a call to the proper function. This isn't
+	// type checked but we already verified types.
+	return &ast.Call{
+		Func: mathFunc,
+		Args: args,
+		Posx: tc.n.Pos(),
+	}, nil
+}
+
 type typeCheckArithmetic struct {
 	n *ast.Arithmetic
 }

config/lang/eval_test.go

@@ -251,6 +251,60 @@ func TestEval(t *testing.T) {
 			"foo 43",
 			ast.TypeString,
 		},
+
+		{
+			"foo ${-46}",
+			nil,
+			false,
+			"foo -46",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${-46 + 5}",
+			nil,
+			false,
+			"foo -41",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${46 + -5}",
+			nil,
+			false,
+			"foo 41",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${-bar}",
+			&ast.BasicScope{
+				VarMap: map[string]ast.Variable{
+					"bar": ast.Variable{
+						Value: 41,
+						Type:  ast.TypeInt,
+					},
+				},
+			},
+			false,
+			"foo -41",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${5 + -bar}",
+			&ast.BasicScope{
+				VarMap: map[string]ast.Variable{
+					"bar": ast.Variable{
+						Value: 41,
+						Type:  ast.TypeInt,
+					},
+				},
+			},
+			false,
+			"foo -36",
+			ast.TypeString,
+		},
 	}
 
 	for _, tc := range cases {

config/lang/lang.y

@@ -130,6 +130,14 @@ expr:
             Posx:  $1.Pos(),
         }
     }
+|   ARITH_OP expr
+    {
+        $$ = &ast.UnaryArithmetic{
+            Op:    $1.Value.(ast.ArithmeticOp),
+            Expr:  $2,
+            Posx:  $1.Pos,
+        }
+    }
 |   IDENTIFIER
     {
         $$ = &ast.VariableAccess{Name: $1.Value.(string), Posx: $1.Pos}

config/lang/lex_test.go

@@ -63,6 +63,20 @@ func TestLex(t *testing.T) {
 				PROGRAM_BRACKET_RIGHT, lexEOF},
 		},
 
+		{
+			"${bar(-42)}",
+			[]int{PROGRAM_BRACKET_LEFT,
+				IDENTIFIER, PAREN_LEFT, ARITH_OP, INTEGER, PAREN_RIGHT,
+				PROGRAM_BRACKET_RIGHT, lexEOF},
+		},
+
+		{
+			"${bar(-42.0)}",
+			[]int{PROGRAM_BRACKET_LEFT,
+				IDENTIFIER, PAREN_LEFT, ARITH_OP, FLOAT, PAREN_RIGHT,
+				PROGRAM_BRACKET_RIGHT, lexEOF},
+		},
+
 		{
 			"${bar(42+1)}",
 			[]int{PROGRAM_BRACKET_LEFT,
@@ -72,6 +86,15 @@ func TestLex(t *testing.T) {
 				PROGRAM_BRACKET_RIGHT, lexEOF},
 		},
 
+		{
+			"${bar(42+-1)}",
+			[]int{PROGRAM_BRACKET_LEFT,
+				IDENTIFIER, PAREN_LEFT,
+				INTEGER, ARITH_OP, ARITH_OP, INTEGER,
+				PAREN_RIGHT,
+				PROGRAM_BRACKET_RIGHT, lexEOF},
+		},
+
 		{
 			"${bar(3.14159)}",
 			[]int{PROGRAM_BRACKET_LEFT,