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builtin.go
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builtin.go
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package eval
import (
"fmt"
"unicode/utf8"
)
type BuiltinFunc func(line string, scope *Scope, args ...Object) Object
type Builtin struct {
Fn BuiltinFunc
}
func (b *Builtin) Inspect() string { return "<builtin function>" }
func (b *Builtin) Type() ObjectType { return BUILTIN_OBJ }
func (b *Builtin) CallMethod(line string, scope *Scope, method string, args ...Object) Object {
return newError(line, ERR_NOMETHOD, method, b.Type())
}
var builtins map[string]*Builtin
func printBuiltin() *Builtin {
return &Builtin{
Fn: func(line string, scope *Scope, args ...Object) Object {
resultStr := ""
for _, arg := range args {
resultStr = resultStr + arg.Inspect()
}
fmt.Fprint(scope.Writer, resultStr)
return NIL
},
}
}
func printlnBuiltin() *Builtin {
return &Builtin{
Fn: func(line string, scope *Scope, args ...Object) Object {
if len(args) == 0 {
fmt.Fprintln(scope.Writer)
}
resultStr := ""
for _, arg := range args {
resultStr = resultStr + arg.Inspect() + "\n"
}
fmt.Fprint(scope.Writer, resultStr)
return NIL
},
}
}
func printfBuiltin() *Builtin {
return &Builtin{
Fn: func(line string, scope *Scope, args ...Object) Object {
if len(args) < 1 {
return newError(line, ERR_ARGUMENT, ">0", len(args))
}
formatObj, ok := args[0].(*String)
if !ok {
return newError(line, ERR_PARAMTYPE, "first", "printf", "*String", args[0].Type())
}
subArgs := args[1:]
wrapped := make([]interface{}, len(subArgs))
for i, v := range subArgs {
wrapped[i] = &Formatter{Obj: v}
}
formatStr := formatObj.String
fmt.Fprintf(scope.Writer, formatStr, wrapped...)
return NIL
},
}
}
func lenBuiltin() *Builtin {
return &Builtin{
Fn: func(line string, scope *Scope, args ...Object) Object {
if len(args) != 1 {
return newError(line, ERR_ARGUMENT, 1, len(args))
}
switch arg := args[0].(type) {
case *String:
n := utf8.RuneCountInString(arg.String)
return NewNumber(float64(n))
case *Array:
return NewNumber(float64(len(arg.Members)))
case *Tuple:
return NewNumber(float64(len(arg.Members)))
case *Hash:
return NewNumber(float64(len(arg.Pairs)))
default:
return newError(line, "argument to `len` not supported, got %s", args[0].Type())
}
},
}
}
func init() {
builtins = map[string]*Builtin{
"print": printBuiltin(),
"println": printlnBuiltin(),
"printf": printfBuiltin(),
"say": printlnBuiltin(),
"len": lenBuiltin(),
}
}