116 lines
2.1 KiB
Go
116 lines
2.1 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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type expression interface{}
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type IOHandle struct {
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Obj expression
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Open bool
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Kind string
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}
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func (i IOHandle) String() string {
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state := "CLOSED"
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if i.Open {
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state = "OPEN"
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}
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return fmt.Sprintf("[%s] io-handle: %s", state, i.Kind)
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}
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type number float64
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type symbol string
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type exception string
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func Parse(s string) expression {
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tokens := Tokenize(s)
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expressions := SplitExpressions(tokens)
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out := make([]expression, 0, len(expressions))
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for i := range expressions {
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out = append(out, parserRead(&expressions[i]))
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}
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return out
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}
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func SplitExpressions(t []string) [][]string {
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counter := 0
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start := 0
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out := make([][]string, 0)
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for i := range t {
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if counter < 0 {
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panic("Too many closing parens found during parsing")
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}
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switch t[i] {
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case "(":
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if counter == 0 {
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start = i
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}
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counter++
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case ")":
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counter--
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if counter == 0 {
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out = append(out, t[start:i+1])
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}
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default:
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if counter == 0 {
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out = append(out, []string{t[i]})
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}
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}
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}
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return out
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}
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func parserRead(tokens *[]string) expression {
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token := (*tokens)[0]
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*tokens = (*tokens)[1:]
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switch token {
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case "(": // parse a list expression
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list := make([]expression, 0)
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for (*tokens)[0] != ")" {
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if t := parserRead(tokens); t != symbol("") {
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list = append(list, t)
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}
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}
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*tokens = (*tokens)[1:]
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return list
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default: // parse an atomic value
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if strings.HasPrefix(token, "0x") {
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i, err := strconv.ParseInt(token[2:], 16, 0)
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if err == nil {
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return number(i)
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}
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}
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if strings.HasPrefix(token, "0") {
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i, err := strconv.ParseInt(token, 8, 0)
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if err == nil {
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return number(i)
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}
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}
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f, err := strconv.ParseFloat(token, 64)
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if err == nil {
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return number(f)
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}
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if strings.HasPrefix(token, "\"") && strings.HasSuffix(token, "\"") {
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return unescapeString(token[1 : len(token)-1])
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} else if strings.HasPrefix(token, "`") && strings.HasSuffix(token, "`") {
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return token[1 : len(token)-1]
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} else if token == "#t" {
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return true
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} else if token == "#f" {
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return false
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} else {
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return symbol(token)
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}
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}
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}
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