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|
package reader
import (
"errors"
"regexp"
"strconv"
//"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)
re := regexp.MustCompile(`[\s,]*(~@|[\[\]{}()'~^@]|"(?:\\.|[^\\"])*"|;.*|[^\s\[\]{}('",;)]*)`)
for _, group := range re.FindAllStringSubmatch(str, -1) {
if group[1] == "" { continue }
results = append(results, group[1])
}
return results
}
func read_atom(rdr Reader) (types.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] == '"' {
// TODO: unquote newline and quotes
return (*token)[1:len(*token)-1], nil
} else if *token == "nil" {
return nil, nil
} else if *token == "true" {
return true, nil
} else if *token == "false" {
return false, nil
} else {
return types.Symbol{*token}, nil
}
return token, nil
}
func read_list(rdr Reader, start string, end string) (types.MalType, error) {
token := rdr.next()
if token == nil { return nil, errors.New("read_list underflow") }
ast_list := []types.MalType{}
if *token != start {
return nil, errors.New("expected '" + start + "'")
}
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 types.List{ast_list}, nil
}
func read_vector(rdr Reader) (types.MalType, error) {
lst, e := read_list(rdr, "[", "]")
if e != nil { return nil, e }
vec := types.Vector{lst.(types.List).Val}
return vec, nil
}
func read_hash_map(rdr Reader) (types.MalType, error) {
mal_lst, e := read_list(rdr, "{", "}")
lst := mal_lst.(types.List).Val
if e != nil { return nil, e }
if len(lst) % 2 == 1 {
return nil, errors.New("Odd number of hash map arguments")
}
m := map[string]types.MalType{}
for i := 0; i < len(lst); i+=2 {
str, ok := lst[i].(string)
if !ok {
return nil, errors.New("expected hash-map key string")
}
m[str] = lst[i+1]
}
return m, nil
}
func read_form(rdr Reader) (types.MalType, error) {
token := rdr.peek()
if token == nil { return nil, errors.New("read_form underflow") }
switch (*token) {
// 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) (types.MalType, error) {
var tokens = tokenize(str);
if len(tokens) == 0 {
return nil, errors.New("<empty line>")
}
return read_form(&TokenReader{tokens: tokens, position: 0})
}
|
