prosper/builtins.go

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package main
import "fmt"
// Builtins is a handy holder for our various default words
type Builtins struct{}
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// ErrExit is a special sentinel value to cease computation and quit
var ErrExit = fmt.Errorf("exit requested")
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// Add sums the top two numbers on the stack and pushes the result
func (b *Builtins) Add(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
r2, err := s.Pop()
if err != nil {
return err
}
s.Push(r1 + r2)
return nil
}
}
// Sub performs NOS - TOS and pushes the result
func (b *Builtins) Sub(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
r2, err := s.Pop()
if err != nil {
return err
}
s.Push(r2 - r1)
return nil
}
}
// Mul multiplies the two numbers on the top of the stack and pushes the result
func (b *Builtins) Mul(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
r2, err := s.Pop()
if err != nil {
return err
}
s.Push(r2 * r1)
return nil
}
}
// Div performs NOS/TOS and pushes the (integer!) result
func (b *Builtins) Div(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
r2, err := s.Pop()
if err != nil {
return err
}
s.Push(r2 / r1)
return nil
}
}
// Print pops the stack and outputs it to stdout
func (b *Builtins) Print(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
fmt.Print(r1, " ")
return nil
}
}
// Dup pops the stack, then pushes two copies onto the stack
func (b *Builtins) Dup(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
s.Push(r1)
s.Push(r1)
return nil
}
}
// Swap inverts the order of TOS and NOS
func (b *Builtins) Swap(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
r2, err := s.Pop()
if err != nil {
return err
}
s.Push(r1)
s.Push(r2)
return nil
}
}
// Over duplicates NOS to TOS, resulting in NOS TOS NOS
func (b *Builtins) Over(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
r2, err := s.Pop()
if err != nil {
return err
}
s.Push(r2)
s.Push(r1)
s.Push(r2)
return nil
}
}
// Drop simply discards TOS
func (b *Builtins) Drop(s *Stack) func() error {
return func() error {
_, err := s.Pop()
return err
}
}
// Rot cycles the first three items on the stack: TOS 1 2 3 -> TOS 3 1 2
func (b *Builtins) Rot(s *Stack) func() error {
return func() error {
r1, err := s.Pop()
if err != nil {
return err
}
r2, err := s.Pop()
if err != nil {
return err
}
r3, err := s.Pop()
if err != nil {
return err
}
s.Push(r2)
s.Push(r1)
s.Push(r3)
return err
}
}
// Words outputs a list of all known words in the dictionary
func (b *Builtins) Words(d Dictionary) func() error {
return func() error {
for n := range d {
fmt.Printf("%s ", n)
}
return nil
}
}
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// Emit outputs the UTF-8 rune for the int on the top of the stack
func (b *Builtins) Emit(s *Stack) func() error {
return func() error {
i, err := s.Pop()
if err != nil {
return err
}
fmt.Print(string(rune(i)) + " ")
return nil
}
}
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// CR prints a newline to standard out
func (b *Builtins) CR() func() error {
return func() error {
fmt.Print("\n")
return nil
}
}
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// Quit exits the repl
func (b *Builtins) Quit() func() error {
return func() error {
return ErrExit
}
}
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// Debug prints the stack without modifying it
func (b *Builtins) Debug(s *Stack) func() error {
return func() error {
fmt.Print(s.values, " ")
return nil
}
}