Add math support to embedded interpolation language

config/lang/ast/arithmetic.go

@@ -0,0 +1,43 @@
+package ast
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// Arithmetic represents a node where the result is arithmetic of
+// two or more operands in the order given.
+type Arithmetic struct {
+	Op    ArithmeticOp
+	Exprs []Node
+	Posx  Pos
+}
+
+func (n *Arithmetic) Accept(v Visitor) Node {
+	for i, expr := range n.Exprs {
+		n.Exprs[i] = expr.Accept(v)
+	}
+
+	return v(n)
+}
+
+func (n *Arithmetic) Pos() Pos {
+	return n.Posx
+}
+
+func (n *Arithmetic) GoString() string {
+	return fmt.Sprintf("*%#v", *n)
+}
+
+func (n *Arithmetic) String() string {
+	var b bytes.Buffer
+	for _, expr := range n.Exprs {
+		b.WriteString(fmt.Sprintf("%s", expr))
+	}
+
+	return b.String()
+}
+
+func (n *Arithmetic) Type(Scope) (Type, error) {
+	return TypeInt, nil
+}

config/lang/ast/arithmetic_op.go

@@ -0,0 +1,13 @@
+package ast
+
+// ArithmeticOp is the operation to use for the math.
+type ArithmeticOp int
+
+const (
+	ArithmeticOpInvalid ArithmeticOp = 0
+	ArithmeticOpAdd     ArithmeticOp = iota
+	ArithmeticOpSub
+	ArithmeticOpMul
+	ArithmeticOpDiv
+	ArithmeticOpMod
+)

config/lang/builtins.go

@@ -15,11 +15,109 @@ func registerBuiltins(scope *ast.BasicScope) *ast.BasicScope {
 	if scope.FuncMap == nil {
 		scope.FuncMap = make(map[string]ast.Function)
 	}
+
+	// Implicit conversions
+	scope.FuncMap["__builtin_FloatToInt"] = builtinFloatToInt()
+	scope.FuncMap["__builtin_FloatToString"] = builtinFloatToString()
+	scope.FuncMap["__builtin_IntToFloat"] = builtinIntToFloat()
 	scope.FuncMap["__builtin_IntToString"] = builtinIntToString()
 	scope.FuncMap["__builtin_StringToInt"] = builtinStringToInt()
+
+	// Math operations
+	scope.FuncMap["__builtin_IntMath"] = builtinIntMath()
+	scope.FuncMap["__builtin_FloatMath"] = builtinFloatMath()
 	return scope
 }
 
+func builtinFloatMath() ast.Function {
+	return ast.Function{
+		ArgTypes:     []ast.Type{ast.TypeInt},
+		Variadic:     true,
+		VariadicType: ast.TypeFloat,
+		ReturnType:   ast.TypeFloat,
+		Callback: func(args []interface{}) (interface{}, error) {
+			op := args[0].(ast.ArithmeticOp)
+			result := args[1].(float64)
+			for _, raw := range args[2:] {
+				arg := raw.(float64)
+				switch op {
+				case ast.ArithmeticOpAdd:
+					result += arg
+				case ast.ArithmeticOpSub:
+					result -= arg
+				case ast.ArithmeticOpMul:
+					result *= arg
+				case ast.ArithmeticOpDiv:
+					result /= arg
+				}
+			}
+
+			return result, nil
+		},
+	}
+}
+
+func builtinIntMath() ast.Function {
+	return ast.Function{
+		ArgTypes:     []ast.Type{ast.TypeInt},
+		Variadic:     true,
+		VariadicType: ast.TypeInt,
+		ReturnType:   ast.TypeInt,
+		Callback: func(args []interface{}) (interface{}, error) {
+			op := args[0].(ast.ArithmeticOp)
+			result := args[1].(int)
+			for _, raw := range args[2:] {
+				arg := raw.(int)
+				switch op {
+				case ast.ArithmeticOpAdd:
+					result += arg
+				case ast.ArithmeticOpSub:
+					result -= arg
+				case ast.ArithmeticOpMul:
+					result *= arg
+				case ast.ArithmeticOpDiv:
+					result /= arg
+				case ast.ArithmeticOpMod:
+					result = result % arg
+				}
+			}
+
+			return result, nil
+		},
+	}
+}
+
+func builtinFloatToInt() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeFloat},
+		ReturnType: ast.TypeInt,
+		Callback: func(args []interface{}) (interface{}, error) {
+			return int(args[0].(float64)), nil
+		},
+	}
+}
+
+func builtinFloatToString() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeFloat},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			return strconv.FormatFloat(
+				args[0].(float64), 'g', -1, 64), nil
+		},
+	}
+}
+
+func builtinIntToFloat() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeInt},
+		ReturnType: ast.TypeFloat,
+		Callback: func(args []interface{}) (interface{}, error) {
+			return float64(args[0].(int)), nil
+		},
+	}
+}
+
 func builtinIntToString() 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.Arithmetic:
+		tc := &typeCheckArithmetic{n}
+		result, err = tc.TypeCheck(v)
 	case *ast.Call:
 		tc := &typeCheckCall{n}
 		result, err = tc.TypeCheck(v)
@@ -70,7 +73,7 @@ func (v *TypeCheck) visit(raw ast.Node) ast.Node {
 	default:
 		tc, ok := raw.(TypeCheckNode)
 		if !ok {
-			err = fmt.Errorf("unknown node: %#v", raw)
+			err = fmt.Errorf("unknown node for type check: %#v", raw)
 			break
 		}
 
@@ -86,6 +89,72 @@ func (v *TypeCheck) visit(raw ast.Node) ast.Node {
 	return result
 }
 
+type typeCheckArithmetic struct {
+	n *ast.Arithmetic
+}
+
+func (tc *typeCheckArithmetic) TypeCheck(v *TypeCheck) (ast.Node, error) {
+	// The arguments are on the stack in reverse order, so pop them off.
+	exprs := make([]ast.Type, len(tc.n.Exprs))
+	for i, _ := range tc.n.Exprs {
+		exprs[len(tc.n.Exprs)-1-i] = v.StackPop()
+	}
+
+	// Determine the resulting type we want
+	mathFunc := "__builtin_IntMath"
+	mathType := ast.TypeInt
+	switch v := exprs[0]; v {
+	case ast.TypeInt:
+		mathFunc = "__builtin_IntMath"
+		mathType = v
+	case ast.TypeFloat:
+		mathFunc = "__builtin_FloatMath"
+		mathType = v
+	default:
+		return nil, fmt.Errorf(
+			"Math operations can only be done with ints and floats, got %s",
+			v)
+	}
+
+	// Verify the args
+	for i, arg := range exprs {
+		if arg != mathType {
+			cn := v.ImplicitConversion(exprs[i], mathType, tc.n.Exprs[i])
+			if cn != nil {
+				tc.n.Exprs[i] = cn
+				continue
+			}
+
+			return nil, fmt.Errorf(
+				"operand %d should be %s, got %s",
+				i+1, mathType, arg)
+		}
+	}
+
+	// Modulo doesn't work for floats
+	if mathType == ast.TypeFloat && tc.n.Op == ast.ArithmeticOpMod {
+		return nil, fmt.Errorf("modulo cannot be used with floats")
+	}
+
+	// Return type
+	v.StackPush(mathType)
+
+	// Replace our node with a call to the proper function. This isn't
+	// type checked but we already verified types.
+	args := make([]ast.Node, len(tc.n.Exprs)+1)
+	args[0] = &ast.LiteralNode{
+		Value: tc.n.Op,
+		Typex: ast.TypeInt,
+		Posx:  tc.n.Pos(),
+	}
+	copy(args[1:], tc.n.Exprs)
+	return &ast.Call{
+		Func: mathFunc,
+		Args: args,
+		Posx: tc.n.Pos(),
+	}, nil
+}
+
 type typeCheckCall struct {
 	n *ast.Call
 }

config/lang/eval.go

@@ -32,7 +32,12 @@ func Eval(root ast.Node, config *EvalConfig) (interface{}, ast.Type, error) {
 	}
 	scope := registerBuiltins(config.GlobalScope)
 	implicitMap := map[ast.Type]map[ast.Type]string{
+		ast.TypeFloat: {
+			ast.TypeInt:    "__builtin_FloatToInt",
+			ast.TypeString: "__builtin_FloatToString",
+		},
 		ast.TypeInt: {
+			ast.TypeFloat:  "__builtin_IntToFloat",
 			ast.TypeString: "__builtin_IntToString",
 		},
 		ast.TypeString: {
@@ -47,7 +52,8 @@ func Eval(root ast.Node, config *EvalConfig) (interface{}, ast.Type, error) {
 	// Build up the semantic checks for execution
 	checks := make(
 		[]SemanticChecker,
-		len(config.SemanticChecks), len(config.SemanticChecks)+2)
+		len(config.SemanticChecks),
+		len(config.SemanticChecks)+2)
 	copy(checks, config.SemanticChecks)
 	checks = append(checks, ic.Visit)
 	checks = append(checks, tv.Visit)

config/lang/eval_test.go

@@ -39,6 +39,101 @@ func TestEval(t *testing.T) {
 			ast.TypeString,
 		},
 
+		{
+			"foo ${42+1}",
+			nil,
+			false,
+			"foo 43",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42-1}",
+			nil,
+			false,
+			"foo 41",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42*2}",
+			nil,
+			false,
+			"foo 84",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42/2}",
+			nil,
+			false,
+			"foo 21",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42%4}",
+			nil,
+			false,
+			"foo 2",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42.0+1.0}",
+			nil,
+			false,
+			"foo 43",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42.0+1}",
+			nil,
+			false,
+			"foo 43",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42+1.0}",
+			nil,
+			false,
+			"foo 43",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42+2*2}",
+			nil,
+			false,
+			"foo 88",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${42+(2*2)}",
+			nil,
+			false,
+			"foo 46",
+			ast.TypeString,
+		},
+
+		{
+			"foo ${bar+1}",
+			&ast.BasicScope{
+				VarMap: map[string]ast.Variable{
+					"bar": ast.Variable{
+						Value: 41,
+						Type:  ast.TypeInt,
+					},
+				},
+			},
+			false,
+			"foo 42",
+			ast.TypeString,
+		},
+
 		{
 			"foo ${rand()}",
 			&ast.BasicScope{