FORTH-ish interpreter
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
prosper/builtins.go

817 lines
18 KiB

package main
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"os"
"strings"
)
// FALSE is a flag for, what else, false
var FALSE = 0
// TRUE is a flag for, what else, true.
// It's -1 because historically, FORTHs would define TRUE as "all bits set to 1 in a cell",
// and interpreting that literally flips the sign flag in a signed integer.
// More generally, TRUE is defined as "not FALSE" for most purposes, and any non-zero integer will work.
var TRUE = -1
// Builtins is a handy holder for our various default words
type Builtins struct{}
// ErrExit is a special sentinel value to cease computation and quit
var ErrExit = fmt.Errorf("exit requested")
// Colon sets the COMPILE/IMMEDIATE flag to COMPILE
func (b *Builtins) Colon(c *Context) func(string) error {
return func(_ string) error {
c.Flags.SetFlag("Immediate", false)
return nil
}
}
// Semicolon sets the COMPILE/IMMEDIATE flag back to IMMEDIATE and adds the defintion to the dictionary
func (b *Builtins) Semicolon(c *Context) func(string) error {
return func(_ string) error {
c.Dictionary.AddWord(c.Words[0], Word{Name: c.Words[0], Source: c.Words[1:]})
c.Words = []string{}
c.Flags.SetFlag("Immediate", true)
return nil
}
}
// OpenComment puts the parser into an "ignore" mode
func (b *Builtins) OpenComment(c *Context) func(string) error {
return func(next string) error {
c.Flags.SetFlag("StashImmediate", c.Flags.GetFlag("Immediate"))
for i := 0; i < len(next); i = i + 1 {
switch next[i] {
case ')':
j, _ := c.RStack.Pop()
c.RStack.Push(j + i - 1) // push the end-point onto the stack
return nil
default:
continue
}
}
return nil
}
}
// EOLComment discards the rest of the parsed line
func (b *Builtins) EOLComment(c *Context) func(string) error {
return func(next string) error {
j, _ := c.RStack.Pop()
c.RStack.Push(j + len(next)) // push the end-point onto the stack
return nil
}
}
// CloseComment resumes parsing by consuming itself and resetting the immediate flag
func (b *Builtins) CloseComment(c *Context) func(string) error {
return func(_ string) error {
c.Flags.SetFlag("Immediate", c.Flags.GetFlag("StashImmediate"))
return nil
}
}
// OpenQuote consumes text until its closing pair to output
func (b *Builtins) OpenQuote(out io.Writer, c *Context, close byte) func(string) error {
if out == nil {
out = os.Stdout
}
return func(next string) error {
c.Flags.SetFlag("StashImmediate", c.Flags.GetFlag("Immediate"))
w := []byte{}
for i := 0; i < len(next); i = i + 1 {
switch next[i] {
case close:
fmt.Fprint(out, string(w))
j, _ := c.RStack.Pop()
c.RStack.Push(j + i - 1) // push the end-point onto the stack
return nil
default:
w = append(w, next[i])
continue
}
}
return nil
}
}
// CloseQuote consumes itself.
func (b *Builtins) CloseQuote(c *Context) func(string) error {
return func(next string) error {
c.Flags.SetFlag("Immediate", c.Flags.GetFlag("StashImmediate"))
return nil
}
}
// StringBuffer consumes text until its closing byte, then puts that value into the context's stringbuffer
func (b *Builtins) StringBuffer(c *Context, close byte) func(string) error {
return func(next string) error {
var buff bytes.Buffer
err := b.OpenQuote(&buff, c, '"')(next)
if err != nil {
return err
}
s, err := ioutil.ReadAll(&buff)
c.StringBuffer = string(s)
return err
}
}
// Eq compares TOS and NOS and puts -1 on the stack if they're equal, 0 otherwise.
func (b *Builtins) Eq(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
if tos == nos {
s.Push(TRUE)
return nil
}
s.Push(FALSE)
return nil
}
}
// NEq compares TOS and NOS and puts -1 on the stack if they're not equal, 0 otherwise.
func (b *Builtins) NEq(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
if tos != nos {
s.Push(TRUE)
return nil
}
s.Push(FALSE)
return nil
}
}
// Lt compares TOS and NOS and puts -1 on the stack if TOS is less than NOS, 0 otherwise.
func (b *Builtins) Lt(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
if nos < tos {
s.Push(TRUE)
return nil
}
s.Push(FALSE)
return nil
}
}
// Gt compares TOS and NOS and puts -1 on the stack if TOS is greater than NOS, 0 otherwise.
func (b *Builtins) Gt(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
if nos > tos {
s.Push(TRUE)
return nil
}
s.Push(FALSE)
return nil
}
}
// LtEq compares TOS and NOS and puts -1 on the stack if TOS is less than or equal to NOS, 0 otherwise.
func (b *Builtins) LtEq(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
if nos <= tos {
s.Push(TRUE)
return nil
}
s.Push(FALSE)
return nil
}
}
// GtEq compares TOS and NOS and puts -1 on the stack if TOS is greater than or equal to NOS, 0 otherwise.
func (b *Builtins) GtEq(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
if nos >= tos {
s.Push(TRUE)
return nil
}
s.Push(FALSE)
return nil
}
}
// Add sums the top two numbers on the stack and pushes the result
func (b *Builtins) Add(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
s.Push(tos + nos)
return nil
}
}
// Sub performs NOS - TOS and pushes the result
func (b *Builtins) Sub(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
s.Push(nos - tos)
return nil
}
}
// Mul multiplies the two numbers on the top of the stack and pushes the result
func (b *Builtins) Mul(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
s.Push(nos * tos)
return nil
}
}
// Div performs NOS/TOS and pushes the (integer!) result
func (b *Builtins) Div(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
s.Push(nos / tos)
return nil
}
}
// Mod performs NOS%TOS and pushes the (integer!) modulo result
func (b *Builtins) Mod(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
s.Push(nos % tos)
return nil
}
}
// Print pops the stack and outputs it to the writer with a trailing space (defaults to stdout)
func (b *Builtins) Print(out io.Writer, s *Stack) func(string) error {
if out == nil {
out = os.Stdout
}
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
fmt.Fprint(out, tos, " ")
return nil
}
}
// Dup pops the stack, then pushes two copies onto the stack
func (b *Builtins) Dup(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
s.Push(tos)
s.Push(tos)
return nil
}
}
// Swap inverts the order of TOS and NOS
func (b *Builtins) Swap(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
s.Push(tos)
s.Push(nos)
return nil
}
}
// Over duplicates NOS to TOS, resulting in NOS TOS NOS
func (b *Builtins) Over(s *Stack) func(string) error {
return func(_ string) error {
nos, err := s.Pick(1)
if err != nil {
return err
}
s.Push(nos)
return nil
}
}
// Drop simply discards TOS
func (b *Builtins) Drop(s *Stack) func(string) error {
return func(_ string) 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(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
p3, err := s.Pop()
if err != nil {
return err
}
s.Push(nos)
s.Push(tos)
s.Push(p3)
return err
}
}
// Pick duplicates TOS from within the stack to the top
func (b *Builtins) Pick(s *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
swp, err := s.Pick(tos)
if err != nil {
return err
}
s.Push(swp)
return nil
}
}
// Words outputs a list of all known words in the dictionary
func (b *Builtins) Words(out io.Writer, d Dictionary) func(string) error {
if out == nil {
out = os.Stdout
}
return func(_ string) error {
for n := range d {
fmt.Fprintf(out, "%s ", n)
}
return nil
}
}
// Flags outputs a list of all flags
func (b *Builtins) Flags(out io.Writer, c *Context) func(string) error {
if out == nil {
out = os.Stdout
}
return func(_ string) error {
for n := range c.Flags {
fmt.Fprintf(out, "%s %v\n", n, c.Flags.GetFlag(n))
}
return nil
}
}
// Emit outputs the UTF-8 rune for the int on the top of the stack
func (b *Builtins) Emit(out io.Writer, s *Stack) func(string) error {
if out == nil {
out = os.Stdout
}
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
fmt.Fprint(out, string(rune(tos))+" ")
return nil
}
}
// ToR pops from the stack to the return stack
func (b *Builtins) ToR(s *Stack, r *Stack) func(string) error {
return func(_ string) error {
tos, err := s.Pop()
if err != nil {
return err
}
r.Push(tos)
return nil
}
}
// RFrom pops from the return stack to the stack
func (b *Builtins) RFrom(s *Stack, r *Stack) func(string) error {
return func(_ string) error {
tors, err := r.Pop()
if err != nil {
return err
}
s.Push(tors)
return nil
}
}
// RFetch copies from the return stack to the stack
func (b *Builtins) RFetch(s *Stack, r *Stack) func(string) error {
return func(_ string) error {
tors, err := r.Pop()
if err != nil {
return err
}
r.Push(tors)
s.Push(tors)
return nil
}
}
// If checks if TOS != 0 and executes any following statements if it is. If TOS == 0, skip execution until ELSE or THEN.
// Nested IFs and ELSE/THENs inside "non-executing" blocks still manipulate the if stack, in order to properly balance
// IFs and THENs. i.e. `0 IF 0 IF 42 EMIT THEN 42 EMIT THEN` should not print anything, but a naive "go until you see any THEN"
// would output "* ".
func (b *Builtins) If(s *Stack, i *Stack) func(string) error {
return func(_ string) error {
// check to see the current IF state. If we're inside a non-executing branch,
// add our own non-execution state, AND tell ELSE to skip its work to boot.
itop, err := i.Pick(0)
if err != nil && !errors.Is(err, ErrUnderflow) {
return err
} else if err == nil && itop == 0 {
i.Push(-1)
return nil
}
tos, err := s.Pop()
if err != nil {
return err
}
// TOS was FALSE, don't execute this branch
if tos == FALSE {
i.Push(0)
return nil
}
// TOS wasn't 0, execute until we see ELSE/THEN
i.Push(1)
return nil
}
}
// Else executes a separate piece of code if the IF stack
func (b *Builtins) Else(i *Stack) func(string) error {
return func(_ string) error {
itop, err := i.Pop()
if err != nil {
return err
}
// don't execute until we see our THEN
if itop == -1 || itop == 1 {
i.Push(0)
}
// we weren't running code, but now we can until THEN
if itop == 0 {
i.Push(1)
}
return nil
}
}
// Then ends an If/Else block
func (b *Builtins) Then(i *Stack) func(string) error {
return func(_ string) error {
// Pop off the existing IF/ELSE state and return
_, err := i.Pop()
return err
}
}
// Do sets up a loop by marking its own location as the return code.
// It also puts TOS and NOS onto the return stack to use as loop control variables.
func (b *Builtins) Do(s *Stack, r *Stack) func(string) error {
return func(_ string) error {
tors, err := r.Pop()
if err != nil {
return err
}
tos, err := s.Pop()
if err != nil {
return err
}
nos, err := s.Pop()
if err != nil {
return err
}
r.Push(nos)
r.Push(tos)
r.Push(tors)
r.Push(tors)
return nil
}
}
// Loop closes a loop by removing its own location from the stack and letting the one that Do inserted get returned.
// If it's reached the end of the loop (checking the loop-control variables _underneath_ the return vars),
// it continues, otherwise it re-adds the original location of the Do and returns.
func (b *Builtins) Loop(s *Stack, r *Stack) func(string) error {
return func(_ string) error {
tors, err := r.Pop()
if err != nil {
return err
}
nors, err := r.Pop()
if err != nil {
return err
}
counter, err := r.Pop()
if err != nil {
return err
}
target, err := r.Pop()
if err != nil {
return err
}
counter = counter + 1
if counter == target {
r.Push(tors)
} else {
r.Push(target)
r.Push(counter)
r.Push(nors)
r.Push(nors)
}
return nil
}
}
// I puts the current value of the loop counter on the top of the stack
func (b *Builtins) I(s *Stack, r *Stack) func(string) error {
return func(_ string) error {
counter, err := r.Pick(2)
if err != nil {
return err
}
s.Push(counter)
return nil
}
}
// Quit exits the repl
func (b *Builtins) Quit() func(string) error {
return func(_ string) error {
return ErrExit
}
}
// Debug prints the stack without modifying it
func (b *Builtins) Debug(out io.Writer, s *Stack) func(string) error {
if out == nil {
out = os.Stdout
}
return func(_ string) error {
fmt.Fprint(out, s.values, " ")
return nil
}
}
// See prints the defintion of a word
func (b *Builtins) See(out io.Writer, r *Stack, d Dictionary) func(string) error {
if out == nil {
out = os.Stdout
}
return func(next string) error {
w := []byte{}
// start at 1, not 0, because a ' ' is the character at 0.
for i := 1; i < len(next); i = i + 1 {
switch next[i] {
case ' ':
word, err := d.GetWord(string(w))
if err != nil {
return err
}
if word.Impl != nil {
fmt.Fprintf(out, "%s [INTERNAL]\n", string(w))
} else {
fmt.Fprintf(out, ": %s %s ;\n", string(w), strings.Join(word.Source, " "))
}
j, err := r.Pop()
r.Push(j + i)
return err
default:
w = append(w, next[i])
continue
}
}
return nil
}
}
// Depth puts the current count of stack items on the stacks
func (b *Builtins) Depth(s *Stack) func(string) error {
return func(_ string) error {
s.Push(len(s.values))
return nil
}
}
// Variable adds a new word to the dictionary that returns a pointer to memory
func (b *Builtins) Variable(c *Context) func(string) error {
return func(next string) error {
w := []byte{}
for i := 1; i < len(next); i = i + 1 {
switch next[i] {
case ' ':
next := c.Memory.NextFreeAddress()
if next == 0 {
// don't use the 0 cell, since we can't distinguish that from the uninitialized field
next = 1
}
c.Dictionary.AddWord(string(w), Word{Name: string(w), Variable: next})
j, _ := c.RStack.Pop()
c.RStack.Push(j + i - 1) // push the end-point onto the stack
return c.Memory.Write(next, []int{0})
default:
w = append(w, next[i])
continue
}
}
return nil
}
}
// Constant adds a new word to the dictionary that puts a value on the stack
func (b *Builtins) Constant(c *Context) func(string) error {
return func(next string) error {
w := []byte{}
for i := 1; i < len(next); i = i + 1 {
switch next[i] {
case ' ':
v, err := c.Stack.Pop()
if err != nil {
return err
}
c.Dictionary.AddWord(string(w), Word{
Name: string(w),
Impl: func(_ string) error {
c.Stack.Push(v)
return nil
},
})
j, _ := c.RStack.Pop()
c.RStack.Push(j + i - 1) // push the end-point onto the stack
return nil
default:
w = append(w, next[i])
continue
}
}
return nil
}
}
// Store places a value in memory
func (b *Builtins) Store(c *Context) func(string) error {
return func(_ string) error {
addr, err := c.Stack.Pop()
if err != nil {
return err
}
val, err := c.Stack.Pop()
if err != nil {
return err
}
return c.Memory.Write(addr, []int{val})
}
}
// Fetch returns a value from memory and puts it on the stack
func (b *Builtins) Fetch(c *Context) func(string) error {
return func(_ string) error {
addr, err := c.Stack.Pop()
if err != nil {
return err
}
res := c.Memory.Read(addr, 1)
c.Stack.Push(res[0])
return nil
}
}
// Load loads a library into the current working environment
func (b *Builtins) Load(c *Context) func(string) error {
return func(_ string) error {
filename := strings.TrimSpace(c.StringBuffer)
if filename == "" {
return fmt.Errorf(`stringbuffer empty; try S" filename.prsp" LOAD`)
}
// store stacks
s, r, i := c.Stack, c.RStack, c.IfStack
c.Stack = &Stack{values: []int{}}
c.RStack = &Stack{values: []int{}}
c.IfStack = &Stack{values: []int{}}
f, err := os.Open(filename)
if err != nil {
return err
}
reader := bufio.NewReader(f)
scanner := bufio.NewScanner(reader)
for {
scan := scanner.Scan()
line := strings.TrimSpace(scanner.Text())
err = c.Eval(line + " ") // append a space to make sure we always close out our parse loop
if err != nil && !errors.Is(err, ErrExit) {
return fmt.Errorf("error in library evaluation: %v", err)
}
if scan == false {
break
}
}
// restore stacks
c.Stack = s
c.RStack = r
c.IfStack = i
return nil
}
}