From 8bb321f8b032dfaeffbe3d1b8dfeb215c12d3642 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Mon, 18 Jul 2022 07:45:58 +0100
Subject: First public release

---
 interpreter/callable.go | 227 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 227 insertions(+)
 create mode 100644 interpreter/callable.go

(limited to 'interpreter/callable.go')

diff --git a/interpreter/callable.go b/interpreter/callable.go
new file mode 100644
index 0000000..e9dc6aa
--- /dev/null
+++ b/interpreter/callable.go
@@ -0,0 +1,227 @@
+package interpreter
+
+import (
+	"fmt"
+
+	"usebox.net/lang/ast"
+	"usebox.net/lang/errors"
+	"usebox.net/lang/tokens"
+)
+
+type Callable interface {
+	Name() string
+	String() string
+	Call(interp *Interpreter, args []any, loc tokens.Location) (any, error)
+	Type() *ast.Type
+	Params() []ast.Type
+	Ret() *ast.Type
+}
+
+var builtInFuncs = map[string]Callable{
+	"len":     builtInLen{},
+	"println": builtInPrintln{},
+	"panic":   builtInPanic{},
+}
+
+func BuiltInTypes() map[string]ast.Type {
+	types := map[string]ast.Type{}
+	for k, v := range builtInFuncs {
+		types[k] = *v.Type()
+	}
+	return types
+}
+
+type builtInLen struct{}
+
+func (n builtInLen) Name() string {
+	return "'len'"
+}
+
+func (n builtInLen) Type() *ast.Type {
+	return ast.NewFuncType(tokens.Token{}, n.Params(), n.Ret())
+}
+
+func (n builtInLen) String() string {
+	return n.Type().String()
+}
+
+func (n builtInLen) Params() []ast.Type {
+	// won't be arity or type checked
+	return []ast.Type{ast.TypeArray}
+}
+
+func (n builtInLen) Ret() *ast.Type {
+	return &ast.TypeNumber
+}
+
+func (n builtInLen) Call(interp *Interpreter, args []any, loc tokens.Location) (any, error) {
+	vals, ok := args[0].([]any)
+	if !ok {
+		// shouldn't happen
+		return nil, errors.NewError(errors.Unexpected, loc, "type mismatch in call to 'len'")
+	}
+	// return
+	panic(&PanicJump{typ: PanicJumpReturn, value: ast.Number(len(vals))})
+}
+
+type builtInPrintln struct{}
+
+func (n builtInPrintln) Name() string {
+	return "'println'"
+}
+
+func (n builtInPrintln) Type() *ast.Type {
+	return ast.NewFuncType(tokens.Token{}, n.Params(), n.Ret())
+}
+
+func (n builtInPrintln) String() string {
+	return n.Type().String()
+}
+
+func (n builtInPrintln) Params() []ast.Type {
+	// won't be arity or type checked
+	return nil
+}
+
+func (n builtInPrintln) Ret() *ast.Type {
+	return &ast.TypeNumber
+}
+
+func (n builtInPrintln) Call(interp *Interpreter, args []any, loc tokens.Location) (any, error) {
+	var count int
+
+	for i := range args {
+		if args[i] == nil {
+			continue
+		}
+		written, err := fmt.Print(args[i])
+		if err != nil {
+			return nil, err
+		}
+		count += written
+	}
+	fmt.Println()
+	count++
+
+	// return
+	panic(&PanicJump{typ: PanicJumpReturn, value: ast.Number(count)})
+}
+
+type builtInPanic struct{}
+
+func (n builtInPanic) Name() string {
+	return "'panic'"
+}
+
+func (n builtInPanic) Type() *ast.Type {
+	return ast.NewFuncType(tokens.Token{}, n.Params(), n.Ret())
+}
+
+func (n builtInPanic) String() string {
+	return n.Type().String()
+}
+
+func (n builtInPanic) Params() []ast.Type {
+	return []ast.Type{ast.TypeString}
+}
+
+func (n builtInPanic) Ret() *ast.Type {
+	// no return (returns none)
+	return nil
+}
+
+func (n builtInPanic) Call(interp *Interpreter, args []any, loc tokens.Location) (any, error) {
+	return nil, fmt.Errorf("[%s] panic: %s", loc, args[0])
+}
+
+type Function struct {
+	fun     ast.Func
+	closure *Env
+}
+
+func (f Function) Name() string {
+	return f.fun.Name.String()
+}
+
+func (f Function) Type() *ast.Type {
+	return ast.NewFuncType(f.fun.Name, f.Params(), f.Ret())
+}
+
+func (f Function) String() string {
+	return f.Type().String()
+}
+
+func (f Function) Params() []ast.Type {
+	params := make([]ast.Type, 0, 1)
+	for _, p := range f.fun.Params {
+		params = append(params, p.Type)
+	}
+	return params
+}
+
+func (f Function) Ret() *ast.Type {
+	return f.fun.Ret
+}
+
+func (f Function) Call(interp *Interpreter, args []any, loc tokens.Location) (result any, err error) {
+	pEnv := interp.env
+	interp.env = NewEnv(f.closure)
+	defer func() {
+		interp.env = pEnv
+	}()
+
+	for n, v := range f.fun.Params {
+		interp.env = interp.env.Set(v.Name.Value, Var{Value: args[n], Loc: v.Name.Loc})
+	}
+
+	// tail call optimization
+	for {
+		// wrap the evaluation in a function
+		var tailCall *PanicJump
+		tailCall, result, err = func() (tailCall *PanicJump, result any, err error) {
+			// handle tail call
+			// will call this function again without setting up a new call frame
+			defer func() {
+				if r := recover(); r != nil {
+					if val, ok := r.(*PanicJump); ok && val.typ == PanicJumpTailCall {
+						tailCall = val
+						return
+					}
+					panic(r)
+				}
+			}()
+			result, err = interp.evaluate(f.fun.Body)
+			return nil, result, err
+		}()
+		if tailCall == nil {
+			break
+		}
+
+		// XXX: can we optimize this?
+		// if the callee can be a variable expression, we probably can't
+		call := tailCall.value.(ast.Call)
+		callee, err := interp.evaluate(call.Callee)
+		if err != nil {
+			return nil, err
+		}
+		if fun, ok := callee.(Callable); !ok || fun.Name() != f.Name() {
+			// can't be optimized
+			val, err := interp.evaluate(call)
+			if err != nil {
+				return nil, err
+			}
+			panic(&PanicJump{typ: PanicJumpReturn, value: val, loc: tailCall.loc})
+		}
+
+		args, err := interp.evalArgs(f.Name(), call.Loc, f.Params(), call.Args)
+		if err != nil {
+			return nil, err
+		}
+
+		for n, v := range f.fun.Params {
+			interp.env.Update(v.Name.Value, args[n])
+		}
+	}
+
+	return result, err
+}
-- 
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