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|
package reader
import (
"errors"
"regexp"
"strconv"
"strings"
//"fmt"
)
import (
. "types"
)
type Reader interface {
next() *string
peek() *string
}
type TokenReader struct {
tokens []string
position int
}
func (tr *TokenReader) next() *string {
if tr.position >= len(tr.tokens) {
return nil
}
token := tr.tokens[tr.position]
tr.position = tr.position + 1
return &token
}
func (tr *TokenReader) peek() *string {
if tr.position >= len(tr.tokens) {
return nil
}
return &tr.tokens[tr.position]
}
func tokenize(str string) []string {
results := make([]string, 0, 1)
// Work around lack of quoting in backtick
re := regexp.MustCompile(`[\s,]*(~@|[\[\]{}()'` + "`" +
`~^@]|"(?:\\.|[^\\"])*"|;.*|[^\s\[\]{}('"` + "`" +
`,;)]*)`)
for _, group := range re.FindAllStringSubmatch(str, -1) {
if (group[1] == "") || (group[1][0] == ';') {
continue
}
results = append(results, group[1])
}
return results
}
func read_atom(rdr Reader) (MalType, error) {
token := rdr.next()
if token == nil {
return nil, errors.New("read_atom underflow")
}
if match, _ := regexp.MatchString(`^-?[0-9]+$`, *token); match {
var i int
var e error
if i, e = strconv.Atoi(*token); e != nil {
return nil, errors.New("number parse error")
}
return i, nil
} else if (*token)[0] == '"' {
str := (*token)[1 : len(*token)-1]
return strings.Replace(
strings.Replace(str, `\"`, `"`, -1),
`\n`, "\n", -1), nil
} else if (*token)[0] == ':' {
return NewKeyword((*token)[1:len(*token)])
} else if *token == "nil" {
return nil, nil
} else if *token == "true" {
return true, nil
} else if *token == "false" {
return false, nil
} else {
return Symbol{*token}, nil
}
return token, nil
}
func read_list(rdr Reader, start string, end string) (MalType, error) {
token := rdr.next()
if token == nil {
return nil, errors.New("read_list underflow")
}
if *token != start {
return nil, errors.New("expected '" + start + "'")
}
ast_list := []MalType{}
token = rdr.peek()
for ; true; token = rdr.peek() {
if token == nil {
return nil, errors.New("exepected '" + end + "', got EOF")
}
if *token == end {
break
}
f, e := read_form(rdr)
if e != nil {
return nil, e
}
ast_list = append(ast_list, f)
}
rdr.next()
return List{ast_list, nil}, nil
}
func read_vector(rdr Reader) (MalType, error) {
lst, e := read_list(rdr, "[", "]")
if e != nil {
return nil, e
}
vec := Vector{lst.(List).Val, nil}
return vec, nil
}
func read_hash_map(rdr Reader) (MalType, error) {
mal_lst, e := read_list(rdr, "{", "}")
if e != nil {
return nil, e
}
return NewHashMap(mal_lst)
}
func read_form(rdr Reader) (MalType, error) {
token := rdr.peek()
if token == nil {
return nil, errors.New("read_form underflow")
}
switch *token {
case `'`:
rdr.next()
form, e := read_form(rdr)
if e != nil {
return nil, e
}
return List{[]MalType{Symbol{"quote"}, form}, nil}, nil
case "`":
rdr.next()
form, e := read_form(rdr)
if e != nil {
return nil, e
}
return List{[]MalType{Symbol{"quasiquote"}, form}, nil}, nil
case `~`:
rdr.next()
form, e := read_form(rdr)
if e != nil {
return nil, e
}
return List{[]MalType{Symbol{"unquote"}, form}, nil}, nil
case `~@`:
rdr.next()
form, e := read_form(rdr)
if e != nil {
return nil, e
}
return List{[]MalType{Symbol{"splice-unquote"}, form}, nil}, nil
case `^`:
rdr.next()
meta, e := read_form(rdr)
if e != nil {
return nil, e
}
form, e := read_form(rdr)
if e != nil {
return nil, e
}
return List{[]MalType{Symbol{"with-meta"}, form, meta}, nil}, nil
case `@`:
rdr.next()
form, e := read_form(rdr)
if e != nil {
return nil, e
}
return List{[]MalType{Symbol{"deref"}, form}, nil}, nil
// list
case ")":
return nil, errors.New("unexpected ')'")
case "(":
return read_list(rdr, "(", ")")
// vector
case "]":
return nil, errors.New("unexpected ']'")
case "[":
return read_vector(rdr)
// hash-map
case "}":
return nil, errors.New("unexpected '}'")
case "{":
return read_hash_map(rdr)
default:
return read_atom(rdr)
}
return read_atom(rdr)
}
func Read_str(str string) (MalType, error) {
var tokens = tokenize(str)
if len(tokens) == 0 {
return nil, errors.New("<empty line>")
}
return read_form(&TokenReader{tokens: tokens, position: 0})
}
|
