func eq(a, b interface{}) interface{} {
var res interface{}
errors.Catch(
func() { res = a == b },
func(_ interface{}) { res = false },
)
return res
}
func catch(thk, hnd interface{}) interface{} {
t, ok := thk.(Function)
if !ok {
TypeError("function", t)
}
h, ok := hnd.(Function)
if !ok {
TypeError("function", h)
}
var res interface{}
errors.Catch(
func() { res = Call(t) },
func(err interface{}) {
e := WrapError(err).(*errorStruct)
res = Call(h, e.kind, e.msg)
},
)
return res
}
func (self *Scope) Repl(in io.Reader, out io.Writer) {
// set stuff up
inp := NewInput(in)
outp := NewOutput(out)
read := func() interface{} {
res := inp.ReadLine()
if res == EOF_OBJECT {
return nil
}
s := res.(string)
if strings.TrimSpace(s) == "" {
return nil
}
res = ReadString(s)
if res == EOF_OBJECT {
return nil
}
return res
}
self.Bind(WrapPrimitives(map[string]interface{}{
"standard-input": func() interface{} { return inp },
"standard-output": func() interface{} { return outp },
}))
// main loop
var x interface{}
for !inp.Eof() {
errors.Catch(
func() {
Display("> ", outp)
outp.Flush()
x = self.Eval(read())
},
func(err interface{}) { x = err },
)
if x != nil {
Write(x, outp)
Display("\n", outp)
}
}
Display("\n", outp)
outp.Flush()
}
func (self *Scope) Expand(x interface{}) interface{} {
done := false
for !done {
p, ok := x.(*Pair)
if !ok {
break
}
if s, ok := p.a.(Symbol); ok {
switch string(s) {
case "quote":
return x
case "if":
return Cons(p.a, self.expandList(p.d))
case "lambda":
{
ctx := NewScope(self)
return Cons(p.a, Cons(Car(p.d), ctx.expandList(Cdr(p.d))))
}
case "set!":
return List(p.a, Car(p.d), self.Expand(Car(Cdr(p.d))))
case "define":
return Cons(p.a, self.expandDefinition(p.d))
case "define-macro":
{
expr := self.expandDefinition(p.d)
expr = List(Symbol("define"), Car(expr), Cons(Symbol("macro"), Cdr(expr)))
self.evalExpr(expr, nil)
return expr
}
case "begin":
return Cons(p.a, self.expandList(p.d))
}
errors.Catch(
func() { x = self.lookupSym(s).(*macro).f.Apply(p.d) },
func(_ interface{}) { x, done = self.expandList(x), true },
)
} else {
x, done = self.expandList(x), true
}
}
return x
}