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builtin.go
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builtin.go
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// This file defines built-in procedures for TopLevel environment.
package scheme
import (
"fmt"
"io/ioutil"
"os"
"strings"
)
var (
builtinProcedures = Binding{
"+": NewSubroutine(plusSubr),
"-": NewSubroutine(minusSubr),
"*": NewSubroutine(multiplySubr),
"/": NewSubroutine(divideSubr),
"=": NewSubroutine(equalSubr),
"<": NewSubroutine(lessThanSubr),
"<=": NewSubroutine(lessEqualSubr),
">": NewSubroutine(greaterThanSubr),
">=": NewSubroutine(greaterEqualSubr),
"append": NewSubroutine(appendSubr),
"boolean?": NewSubroutine(isBooleanSubr),
"car": NewSubroutine(carSubr),
"cdr": NewSubroutine(cdrSubr),
"cons": NewSubroutine(consSubr),
"dump": NewSubroutine(dumpSubr),
"eq?": NewSubroutine(isEqSubr),
"equal?": NewSubroutine(isEqualSubr),
"exit": NewSubroutine(exitSubr),
"last": NewSubroutine(lastSubr),
"length": NewSubroutine(lengthSubr),
"list": NewSubroutine(listSubr),
"list?": NewSubroutine(isListSubr),
"load": NewSubroutine(loadSubr),
"memq": NewSubroutine(memqSubr),
"neq?": NewSubroutine(isNeqSubr),
"number?": NewSubroutine(isNumberSubr),
"number->string": NewSubroutine(numberToStringSubr),
"pair?": NewSubroutine(isPairSubr),
"print": NewSubroutine(printSubr),
"procedure?": NewSubroutine(isProcedureSubr),
"set-car!": NewSubroutine(setCarSubr),
"set-cdr!": NewSubroutine(setCdrSubr),
"string?": NewSubroutine(isStringSubr),
"string-append": NewSubroutine(stringAppendSubr),
"string->number": NewSubroutine(stringToNumberSubr),
"string->symbol": NewSubroutine(stringToSymbolSubr),
"symbol?": NewSubroutine(isSymbolSubr),
"symbol->string": NewSubroutine(symbolToStringSubr),
"write": NewSubroutine(writeSubr),
}
)
func carSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
object := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(object, "pair")
return object.(*Pair).Car
}
func cdrSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
object := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(object, "pair")
return object.(*Pair).Cdr
}
func consSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 2)
objects := evaledObjects(arguments.(*Pair).Elements())
return &Pair{
ObjectBase: ObjectBase{parent: arguments.Parent()},
Car: objects[0],
Cdr: objects[1],
}
}
func divideSubr(s *Subroutine, arguments Object) Object {
assertListMinimum(arguments, 1)
numbers := evaledObjects(arguments.(*Pair).Elements())
assertObjectsType(numbers, "number")
quotient := numbers[0].(*Number).value
for _, number := range numbers[1:] {
quotient /= number.(*Number).value
}
return NewNumber(quotient)
}
func dumpSubr(s *Subroutine, arguments Object) Object {
object := arguments.(*Pair).ElementAt(0).Eval()
fmt.Printf("%d\n", object)
return undef
}
func equalSubr(s *Subroutine, arguments Object) Object {
return s.compareNumbers(arguments, func(a, b int) bool { return a == b })
}
func exitSubr(s *Subroutine, arguments Object) Object {
os.Exit(0)
return undef
}
func greaterThanSubr(s *Subroutine, arguments Object) Object {
return s.compareNumbers(arguments, func(a, b int) bool { return a > b })
}
func greaterEqualSubr(s *Subroutine, arguments Object) Object {
return s.compareNumbers(arguments, func(a, b int) bool { return a >= b })
}
func lengthSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
list := arguments.(*Pair).ElementAt(0).Eval()
assertListMinimum(list, 0)
return NewNumber(list.(*Pair).ListLength())
}
func lessEqualSubr(s *Subroutine, arguments Object) Object {
return s.compareNumbers(arguments, func(a, b int) bool { return a <= b })
}
func lessThanSubr(s *Subroutine, arguments Object) Object {
return s.compareNumbers(arguments, func(a, b int) bool { return a < b })
}
func listSubr(s *Subroutine, arguments Object) Object {
return arguments
}
func memqSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 2)
searchObject := arguments.(*Pair).ElementAt(0).Eval()
list := arguments.(*Pair).ElementAt(1).Eval()
for {
switch list.(type) {
case *Pair:
if areIdentical(list.(*Pair).Car, searchObject) {
return list
}
default:
break
}
if list = list.(*Pair).Cdr; list == nil {
break
}
}
return NewBoolean(false)
}
func minusSubr(s *Subroutine, arguments Object) Object {
assertListMinimum(arguments, 1)
numbers := evaledObjects(arguments.(*Pair).Elements())
assertObjectsType(numbers, "number")
difference := numbers[0].(*Number).value
for _, number := range numbers[1:] {
difference -= number.(*Number).value
}
return NewNumber(difference)
}
func multiplySubr(s *Subroutine, arguments Object) Object {
assertListMinimum(arguments, 0)
numbers := evaledObjects(arguments.(*Pair).Elements())
assertObjectsType(numbers, "number")
product := 1
for _, number := range numbers {
product *= number.(*Number).value
}
return NewNumber(product)
}
func lastSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
list := arguments.(*Pair).ElementAt(0).Eval()
if !list.isPair() {
runtimeError("pair required: %s", list)
}
assertListMinimum(list, 1)
elements := list.(*Pair).Elements()
return elements[len(elements)-1].Eval()
}
func appendSubr(s *Subroutine, arguments Object) Object {
assertListMinimum(arguments, 0)
elements := evaledObjects(arguments.(*Pair).Elements())
appendedList := NewPair(arguments)
for _, element := range elements {
appendedList = appendedList.AppendList(element)
}
return appendedList
}
func numberToStringSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
object := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(object, "number")
return NewString(object.(*Number).value)
}
func isBooleanSubr(s *Subroutine, arguments Object) Object {
return s.booleanByFunc(arguments, func(object Object) bool { return object.isBoolean() })
}
func isEqSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 2)
objects := evaledObjects(arguments.(*Pair).Elements())
return NewBoolean(areIdentical(objects[0], objects[1]))
}
func isEqualSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 2)
objects := evaledObjects(arguments.(*Pair).Elements())
return NewBoolean(areEqual(objects[0], objects[1]))
}
func isListSubr(s *Subroutine, arguments Object) Object {
return s.booleanByFunc(arguments, func(object Object) bool { return object.isList() })
}
func isNeqSubr(s *Subroutine, arguments Object) Object {
return NewBoolean(!isEqSubr(s, arguments).(*Boolean).value)
}
func isNumberSubr(s *Subroutine, arguments Object) Object {
return s.booleanByFunc(arguments, func(object Object) bool { return object.isNumber() })
}
func isPairSubr(s *Subroutine, arguments Object) Object {
return s.booleanByFunc(arguments, func(object Object) bool { return object.isPair() })
}
func isProcedureSubr(s *Subroutine, arguments Object) Object {
return s.booleanByFunc(arguments, func(object Object) bool { return object.isProcedure() })
}
func isSymbolSubr(s *Subroutine, arguments Object) Object {
return s.booleanByFunc(arguments, func(object Object) bool { return object.isSymbol() })
}
func isStringSubr(s *Subroutine, arguments Object) Object {
return s.booleanByFunc(arguments, func(object Object) bool { return object.isString() })
}
func loadSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
object := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(object, "string")
buffer, err := ioutil.ReadFile(object.(*String).text)
if err != nil {
runtimeError("cannot find \"%s\"", object.(*String).text)
return nil
}
parser := NewParser(string(buffer))
parser.Peek()
for _, e := range parser.Parse(arguments.Parent()) {
e.Eval()
}
return NewBoolean(true)
}
func plusSubr(s *Subroutine, arguments Object) Object {
assertListMinimum(arguments, 0)
numbers := evaledObjects(arguments.(*Pair).Elements())
assertObjectsType(numbers, "number")
sum := 0
for _, number := range numbers {
sum += number.(*Number).value
}
return NewNumber(sum)
}
func printSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1) // TODO: accept output port
object := arguments.(*Pair).ElementAt(0).Eval()
if object.isString() {
fmt.Printf("%s\n", object.(*String).text)
} else {
fmt.Printf("%s\n", object)
}
return undef
}
func setCarSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 2)
object := arguments.(*Pair).ElementAt(1).Eval()
pair := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(pair, "pair")
pair.(*Pair).Car = object
return undef
}
func setCdrSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 2)
object := arguments.(*Pair).ElementAt(1).Eval()
pair := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(pair, "pair")
pair.(*Pair).Cdr = object
return undef
}
func stringAppendSubr(s *Subroutine, arguments Object) Object {
assertListMinimum(arguments, 0)
stringObjects := evaledObjects(arguments.(*Pair).Elements())
assertObjectsType(stringObjects, "string")
texts := []string{}
for _, stringObject := range stringObjects {
texts = append(texts, stringObject.(*String).text)
}
return NewString(strings.Join(texts, ""))
}
func stringToNumberSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
object := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(object, "string")
return NewNumber(object.(*String).text)
}
func symbolToStringSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
object := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(object, "symbol")
return NewString(object.(*Symbol).identifier)
}
func stringToSymbolSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1)
object := arguments.(*Pair).ElementAt(0).Eval()
assertObjectType(object, "string")
return NewSymbol(object.(*String).text)
}
func writeSubr(s *Subroutine, arguments Object) Object {
assertListEqual(arguments, 1) // TODO: accept output port
object := arguments.(*Pair).ElementAt(0).Eval()
fmt.Printf("%s", object)
return undef
}