96 lines
2.0 KiB
Go
96 lines
2.0 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 + Stack representing a runtime environment
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type Context struct {
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Dictionary Dictionary
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Stack *Stack
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RStack *Stack
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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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var comment bool
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immediate := true
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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 '(', ')': // comments
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if len(word) == 0 {
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if line[i] == '(' {
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comment = true
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continue
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}
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comment = false
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continue
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} else {
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word = append(word, line[i])
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}
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case ':', ';': // COMPILE/IMMEDIATE mode swapping
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if len(word) == 0 {
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if line[i] == ':' {
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immediate = false
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}
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} else {
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if line[i-1] == ' ' && line[i] == ';' {
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def := strings.SplitN(strings.TrimSpace(string(word)), " ", 2)
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c.Dictionary.AddWord(def[0], nil, def[1]+" ")
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word = []byte{}
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immediate = true
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} else {
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word = append(word, line[i])
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}
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}
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case ' ':
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if !immediate { // continue building our subroutine if we're not in immediate mode...
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word = append(word, line[i])
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continue
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}
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if len(word) == 0 || comment {
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// empty space, just continue...
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continue
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}
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int, err := strconv.Atoi(string(word))
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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(int)
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word = []byte{}
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continue
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}
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// it wasn't a number. Is it a word we know?
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w, err := c.Dictionary.GetWord(string(word))
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if err != nil {
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return fmt.Errorf("could not parse %s; %v", w.Name, err)
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}
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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()
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if err != nil {
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return err
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}
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word = []byte{}
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} else if w.Source != "" {
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// user-defined word; let's descend...
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err := c.Eval(w.Source)
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if err != nil {
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return err
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}
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word = []byte{}
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}
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default:
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if !comment {
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word = append(word, line[i])
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}
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}
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}
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return nil
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}
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