96 lines
2.3 KiB
Go
96 lines
2.3 KiB
Go
package main
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import (
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"fmt"
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"strconv"
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"strings"
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)
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// Context is a set of Dictionary + Stacks + Flags representing a runtime environment
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type Context struct {
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Dictionary Dictionary
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Stack *Stack // main stack
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RStack *Stack // "return" stack, for handling loops/backward jumps
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IfStack *Stack // tracks nested branches
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Flags Flags
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Words []string
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Memory Memory
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}
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// Eval evaulates a given line, recursively descending into given words as needed
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func (c *Context) Eval(line string) error {
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// state
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var word []byte
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for i := 0; i < len(line); i = i + 1 {
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switch line[i] {
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case ' ':
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sword := strings.TrimSpace(string(word))
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if len(word) == 0 {
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// empty space, just continue...
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continue
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}
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// Is this a word we know?
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w, _ := c.Dictionary.GetWord(sword)
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// check if it's an IMMEDIATE mode toggle word
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if !c.Flags.GetFlag("Immediate") {
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c.Flags.SetFlag("Immediate", w.Immediate)
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}
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if !c.Flags.GetFlag("Immediate") {
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c.Words = append(c.Words, sword)
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word = []byte{}
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continue
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}
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ifcheck, _ := c.IfStack.Pick(0)
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if len(c.IfStack.values) == 0 || (len(c.IfStack.values) > 0 && ifcheck == 1) || w.BranchCheck {
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// run word
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c.RStack.Push(i)
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err := c.Exec(w, line[i:])
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if err != nil {
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return err
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}
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i, err = c.RStack.Pop()
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if err != nil {
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return fmt.Errorf("error while popping from return stack: %v", err)
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}
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}
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word = []byte{}
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default:
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word = append(word, line[i])
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}
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}
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return nil
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}
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// Exec wraps the branched execution of words (either built-in or user-defined)
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func (c *Context) Exec(w Word, s string) error {
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if w.Impl != nil {
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// we have an implementation for that word. Run it.
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err := w.Impl(s)
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if err != nil {
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return fmt.Errorf("error during built-in: %w", err)
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}
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} else if len(w.Source) != 0 {
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// user-defined word; let's descend...
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err := c.Eval(strings.Join(w.Source, " ") + " ")
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if err != nil {
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return fmt.Errorf("error during nested evaluation of word %+v: %w", w, err)
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}
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} else if w.Variable > 0 {
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// it's a variable, let's get that address and put it on the stack
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c.Stack.Push(w.Variable)
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} else {
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it, err := strconv.Atoi(w.Name)
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if err == nil {
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// it was a number! put it on the stack.
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c.Stack.Push(it)
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} else {
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return fmt.Errorf("unable to parse word %s", w.Name)
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}
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}
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return nil
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}
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