mirror of
https://codeberg.org/superseriousbusiness/gotosocial.git
synced 2024-12-21 16:34:26 +03:00
313 lines
7.1 KiB
Go
313 lines
7.1 KiB
Go
package expr
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import (
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`strconv`
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`unicode`
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`unsafe`
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)
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type _TokenKind uint8
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const (
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_T_end _TokenKind = iota + 1
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_T_int
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_T_punc
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_T_name
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)
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const (
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_OP2 = 0x80
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_POW = _OP2 | '*'
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_SHL = _OP2 | '<'
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_SHR = _OP2 | '>'
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)
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type _Slice struct {
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p unsafe.Pointer
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n int
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c int
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}
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type _Token struct {
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pos int
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ptr *rune
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u64 uint64
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tag _TokenKind
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}
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func (self _Token) str() (v string) {
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return string(self.rbuf())
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}
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func (self _Token) rbuf() (v []rune) {
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(*_Slice)(unsafe.Pointer(&v)).c = int(self.u64)
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(*_Slice)(unsafe.Pointer(&v)).n = int(self.u64)
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(*_Slice)(unsafe.Pointer(&v)).p = unsafe.Pointer(self.ptr)
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return
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}
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func tokenEnd(p int) _Token {
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return _Token {
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pos: p,
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tag: _T_end,
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}
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}
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func tokenInt(p int, v uint64) _Token {
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return _Token {
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pos: p,
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u64: v,
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tag: _T_int,
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}
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}
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func tokenPunc(p int, v rune) _Token {
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return _Token {
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pos: p,
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tag: _T_punc,
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u64: uint64(v),
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}
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}
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func tokenName(p int, v []rune) _Token {
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return _Token {
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pos: p,
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ptr: &v[0],
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tag: _T_name,
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u64: uint64(len(v)),
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}
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}
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// Repository represents a repository of Term's.
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type Repository interface {
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Get(name string) (Term, error)
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}
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// Parser parses an expression string to it's AST representation.
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type Parser struct {
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pos int
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src []rune
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}
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var binaryOps = [...]func(*Expr, *Expr) *Expr {
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'+' : (*Expr).Add,
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'-' : (*Expr).Sub,
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'*' : (*Expr).Mul,
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'/' : (*Expr).Div,
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'%' : (*Expr).Mod,
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'&' : (*Expr).And,
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'^' : (*Expr).Xor,
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'|' : (*Expr).Or,
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_SHL : (*Expr).Shl,
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_SHR : (*Expr).Shr,
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_POW : (*Expr).Pow,
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}
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var precedence = [...]map[int]bool {
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{_SHL: true, _SHR: true},
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{'|' : true},
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{'^' : true},
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{'&' : true},
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{'+' : true, '-': true},
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{'*' : true, '/': true, '%': true},
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{_POW: true},
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}
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func (self *Parser) ch() rune {
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return self.src[self.pos]
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}
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func (self *Parser) eof() bool {
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return self.pos >= len(self.src)
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}
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func (self *Parser) rch() (v rune) {
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v, self.pos = self.src[self.pos], self.pos + 1
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return
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}
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func (self *Parser) hex(ss []rune) bool {
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if len(ss) == 1 && ss[0] == '0' {
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return unicode.ToLower(self.ch()) == 'x'
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} else if len(ss) <= 1 || unicode.ToLower(ss[1]) != 'x' {
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return unicode.IsDigit(self.ch())
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} else {
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return ishexdigit(self.ch())
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}
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}
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func (self *Parser) int(p int, ss []rune) (_Token, error) {
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var err error
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var val uint64
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/* find all the digits */
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for !self.eof() && self.hex(ss) {
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ss = append(ss, self.rch())
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}
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/* parse the value */
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if val, err = strconv.ParseUint(string(ss), 0, 64); err != nil {
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return _Token{}, err
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} else {
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return tokenInt(p, val), nil
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}
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}
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func (self *Parser) name(p int, ss []rune) _Token {
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for !self.eof() && isident(self.ch()) { ss = append(ss, self.rch()) }
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return tokenName(p, ss)
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}
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func (self *Parser) read(p int, ch rune) (_Token, error) {
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if isdigit(ch) {
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return self.int(p, []rune { ch })
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} else if isident0(ch) {
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return self.name(p, []rune { ch }), nil
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} else if isop2ch(ch) && !self.eof() && self.ch() == ch {
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return tokenPunc(p, _OP2 | self.rch()), nil
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} else if isop1ch(ch) {
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return tokenPunc(p, ch), nil
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} else {
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return _Token{}, newSyntaxError(self.pos, "invalid character " + strconv.QuoteRuneToASCII(ch))
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}
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}
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func (self *Parser) next() (_Token, error) {
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for {
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var p int
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var c rune
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/* check for EOF */
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if self.eof() {
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return tokenEnd(self.pos), nil
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}
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/* read the next char */
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p = self.pos
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c = self.rch()
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/* parse the token if not a space */
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if !unicode.IsSpace(c) {
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return self.read(p, c)
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}
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}
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}
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func (self *Parser) grab(tk _Token, repo Repository) (*Expr, error) {
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if repo == nil {
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return nil, newSyntaxError(tk.pos, "unresolved symbol: " + tk.str())
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} else if term, err := repo.Get(tk.str()); err != nil {
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return nil, err
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} else {
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return Ref(term), nil
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}
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}
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func (self *Parser) nest(nest int, repo Repository) (*Expr, error) {
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var err error
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var ret *Expr
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var ntk _Token
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/* evaluate the nested expression */
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if ret, err = self.expr(0, nest + 1, repo); err != nil {
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return nil, err
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}
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/* must follows with a ')' */
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if ntk, err = self.next(); err != nil {
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return nil, err
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} else if ntk.tag != _T_punc || ntk.u64 != ')' {
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return nil, newSyntaxError(ntk.pos, "')' expected")
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} else {
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return ret, nil
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}
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}
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func (self *Parser) unit(nest int, repo Repository) (*Expr, error) {
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if tk, err := self.next(); err != nil {
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return nil, err
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} else if tk.tag == _T_int {
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return Int(int64(tk.u64)), nil
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} else if tk.tag == _T_name {
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return self.grab(tk, repo)
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} else if tk.tag == _T_punc && tk.u64 == '(' {
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return self.nest(nest, repo)
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} else if tk.tag == _T_punc && tk.u64 == '+' {
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return self.unit(nest, repo)
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} else if tk.tag == _T_punc && tk.u64 == '-' {
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return neg2(self.unit(nest, repo))
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} else if tk.tag == _T_punc && tk.u64 == '~' {
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return not2(self.unit(nest, repo))
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} else {
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return nil, newSyntaxError(tk.pos, "integer, unary operator or nested expression expected")
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}
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}
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func (self *Parser) term(prec int, nest int, repo Repository) (*Expr, error) {
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var err error
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var val *Expr
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/* parse the LHS operand */
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if val, err = self.expr(prec + 1, nest, repo); err != nil {
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return nil, err
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}
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/* parse all the operators of the same precedence */
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for {
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var op int
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var rv *Expr
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var tk _Token
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/* peek the next token */
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pp := self.pos
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tk, err = self.next()
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/* check for errors */
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if err != nil {
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return nil, err
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}
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/* encountered EOF */
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if tk.tag == _T_end {
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return val, nil
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}
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/* must be an operator */
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if tk.tag != _T_punc {
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return nil, newSyntaxError(tk.pos, "operators expected")
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}
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/* check for the operator precedence */
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if op = int(tk.u64); !precedence[prec][op] {
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self.pos = pp
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return val, nil
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}
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/* evaluate the RHS operand, and combine the value */
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if rv, err = self.expr(prec + 1, nest, repo); err != nil {
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return nil, err
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} else {
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val = binaryOps[op](val, rv)
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}
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}
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}
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func (self *Parser) expr(prec int, nest int, repo Repository) (*Expr, error) {
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if prec >= len(precedence) {
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return self.unit(nest, repo)
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} else {
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return self.term(prec, nest, repo)
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}
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}
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// Parse parses the expression, and returns it's AST tree.
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func (self *Parser) Parse(repo Repository) (*Expr, error) {
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return self.expr(0, 0, repo)
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}
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// SetSource resets the expression parser and sets the expression source.
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func (self *Parser) SetSource(src string) *Parser {
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self.pos = 0
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self.src = []rune(src)
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return self
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}
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