ginger/expr/expr.go

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package expr
import (
"fmt"
"io"
"strconv"
"strings"
"github.com/mediocregopher/ginger/lexer"
)
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// TODO doc strings
// TODO empty blocks
// TODO empty parenthesis
type tok lexer.Token
func (t tok) Token() lexer.Token {
return lexer.Token(t)
}
type Expr interface {
Token() lexer.Token
String() string
// Equal should return true if the type and value of the other expression
// are equal. The tokens shouldn't be taken into account
Equal(Expr) bool
}
////////////////////////////////////////////////////////////////////////////////
type Bool struct {
tok
val bool
}
func (b Bool) String() string {
return fmt.Sprint(b.val)
}
func (b Bool) Equal(e Expr) bool {
bb, ok := e.(Bool)
if !ok {
return false
}
return bb.val == b.val
}
////////////////////////////////////////////////////////////////////////////////
type Int struct {
tok
val int64
}
func (i Int) String() string {
return fmt.Sprint(i.val)
}
func (i Int) Equal(e Expr) bool {
ii, ok := e.(Int)
if !ok {
return false
}
return ii.val == i.val
}
////////////////////////////////////////////////////////////////////////////////
type String struct {
tok
str string
}
func (s String) String() string {
return strconv.QuoteToASCII(s.str)
}
func (s String) Equal(e Expr) bool {
ss, ok := e.(String)
if !ok {
return false
}
return ss.str == s.str
}
////////////////////////////////////////////////////////////////////////////////
type Identifier struct {
tok
ident string
}
func (id Identifier) String() string {
return id.ident
}
func (id Identifier) Equal(e Expr) bool {
idid, ok := e.(Identifier)
if !ok {
return false
}
return idid.ident == id.ident
}
////////////////////////////////////////////////////////////////////////////////
type Tuple struct {
exprs []Expr
}
func (tup Tuple) Token() lexer.Token {
return tup.exprs[0].Token()
}
func (tup Tuple) String() string {
strs := make([]string, len(tup.exprs))
for i := range tup.exprs {
strs[i] = tup.exprs[i].String()
}
return "(" + strings.Join(strs, ", ") + ")"
}
func (tup Tuple) Equal(e Expr) bool {
tuptup, ok := e.(Tuple)
if !ok || len(tuptup.exprs) != len(tup.exprs) {
return false
}
for i := range tup.exprs {
if !tup.exprs[i].Equal(tuptup.exprs[i]) {
return false
}
}
return true
}
////////////////////////////////////////////////////////////////////////////////
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type Pipe struct {
exprs []Expr
}
func (p Pipe) Token() lexer.Token {
return p.exprs[0].Token()
}
func (p Pipe) String() string {
strs := make([]string, len(p.exprs))
for i := range p.exprs {
strs[i] = p.exprs[i].String()
}
return "(" + strings.Join(strs, "|") + ")"
}
func (p Pipe) Equal(e Expr) bool {
pp, ok := e.(Pipe)
if !ok || len(pp.exprs) != len(p.exprs) {
return false
}
for i := range p.exprs {
if !p.exprs[i].Equal(pp.exprs[i]) {
return false
}
}
return true
}
////////////////////////////////////////////////////////////////////////////////
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type Statement struct {
in Expr
pipe Pipe
}
func (s Statement) Token() lexer.Token {
return s.in.Token()
}
func (s Statement) String() string {
return fmt.Sprintf("(%s > %s)", s.in.String(), s.pipe.String())
}
func (s Statement) Equal(e Expr) bool {
ss, ok := e.(Statement)
return ok && s.in.Equal(ss.in) && s.pipe.Equal(ss.pipe)
}
////////////////////////////////////////////////////////////////////////////////
type Block struct {
stmts []Statement
}
func (b Block) Token() lexer.Token {
return b.stmts[0].Token()
}
func (b Block) String() string {
strs := make([]string, len(b.stmts))
for i := range b.stmts {
strs[i] = b.stmts[i].String()
}
return fmt.Sprintf("{ %s }", strings.Join(strs, " "))
}
func (b Block) Equal(e Expr) bool {
bb, ok := e.(Block)
if !ok {
return false
}
for i := range b.stmts {
if !b.stmts[i].Equal(bb.stmts[i]) {
return false
}
}
return true
}
////////////////////////////////////////////////////////////////////////////////
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type exprErr struct {
reason string
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err error
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tok lexer.Token
tokCtx string // e.g. "block starting at" or "open paren at"
}
func (e exprErr) Error() string {
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var msg string
if e.err != nil {
msg = e.err.Error()
} else {
msg = e.reason
}
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if err := e.tok.Err(); err != nil {
msg += " - token error: " + err.Error()
} else if (e.tok != lexer.Token{}) {
msg += " - "
if e.tokCtx != "" {
msg += e.tokCtx + ": "
}
msg = fmt.Sprintf("%s [line:%d col:%d]", msg, e.tok.Row, e.tok.Col)
}
return msg
}
////////////////////////////////////////////////////////////////////////////////
// toks[0] must be start
func sliceEnclosedToks(toks []lexer.Token, start, end lexer.Token) ([]lexer.Token, []lexer.Token, error) {
c := 1
ret := []lexer.Token{}
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first := toks[0]
for i, tok := range toks[1:] {
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if tok.Err() != nil {
return nil, nil, exprErr{
reason: fmt.Sprintf("missing closing %v", end),
tok: tok,
}
}
if tok.Equal(start) {
c++
} else if tok.Equal(end) {
c--
}
if c == 0 {
return ret, toks[2+i:], nil
}
ret = append(ret, tok)
}
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return nil, nil, exprErr{
reason: fmt.Sprintf("missing closing %v", end),
tok: first,
tokCtx: "starting at",
}
}
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// Parse reads in all expressions it can from the given io.Reader and returns
// them
func Parse(r io.Reader) ([]Expr, error) {
toks := readAllToks(r)
var ret []Expr
var expr Expr
var err error
for len(toks) > 0 {
if toks[0].TokenType == lexer.EOF {
return ret, nil
}
expr, toks, err = parse(toks)
if err != nil {
return nil, err
}
ret = append(ret, expr)
}
return ret, nil
}
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// ParseAsBlock reads the given io.Reader as if it was implicitly surrounded by
// curly braces, making it into a Block. This means all expressions from the
// io.Reader *must* be statements
func ParseAsBlock(r io.Reader) (Block, error) {
return parseBlock(readAllToks(r))
}
func readAllToks(r io.Reader) []lexer.Token {
l := lexer.New(r)
var toks []lexer.Token
for l.HasNext() {
toks = append(toks, l.Next())
}
return toks
}
// For all parse methods it is assumed that toks is not empty
var (
openParen = lexer.Token{TokenType: lexer.Wrapper, Val: "("}
closeParen = lexer.Token{TokenType: lexer.Wrapper, Val: ")"}
openCurly = lexer.Token{TokenType: lexer.Wrapper, Val: "{"}
closeCurly = lexer.Token{TokenType: lexer.Wrapper, Val: "}"}
comma = lexer.Token{TokenType: lexer.Punctuation, Val: ","}
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pipe = lexer.Token{TokenType: lexer.Punctuation, Val: "|"}
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arrow = lexer.Token{TokenType: lexer.Punctuation, Val: ">"}
)
func parse(toks []lexer.Token) (Expr, []lexer.Token, error) {
expr, toks, err := parseSingle(toks)
if err != nil {
return nil, nil, err
}
if len(toks) > 0 && toks[0].TokenType == lexer.Punctuation {
return parseConnectingPunct(toks, expr)
}
return expr, toks, nil
}
func parseSingle(toks []lexer.Token) (Expr, []lexer.Token, error) {
var expr Expr
var err error
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if toks[0].Err() != nil {
return nil, nil, exprErr{
reason: "could not parse token",
tok: toks[0],
}
}
if toks[0].Equal(openParen) {
starter := toks[0]
var ptoks []lexer.Token
ptoks, toks, err = sliceEnclosedToks(toks, openParen, closeParen)
if err != nil {
return nil, nil, err
}
if expr, ptoks, err = parse(ptoks); err != nil {
return nil, nil, err
} else if len(ptoks) > 0 {
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return nil, nil, exprErr{
reason: "multiple expressions inside parenthesis",
tok: starter,
tokCtx: "starting at",
}
}
return expr, toks, nil
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} else if toks[0].Equal(openCurly) {
var btoks []lexer.Token
btoks, toks, err = sliceEnclosedToks(toks, openCurly, closeCurly)
if err != nil {
return nil, nil, err
}
if expr, err = parseBlock(btoks); err != nil {
return nil, nil, err
}
return expr, toks, nil
}
if expr, err = parseNonPunct(toks[0]); err != nil {
return nil, nil, err
}
return expr, toks[1:], nil
}
func parseNonPunct(tok lexer.Token) (Expr, error) {
if tok.TokenType == lexer.Identifier {
return parseIdentifier(tok)
} else if tok.TokenType == lexer.String {
return parseString(tok)
}
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return nil, exprErr{
reason: "unexpected non-punctuation token",
tok: tok,
}
}
func parseIdentifier(t lexer.Token) (Expr, error) {
if t.Val[0] == '-' || (t.Val[0] >= '0' && t.Val[0] <= '9') {
n, err := strconv.ParseInt(t.Val, 10, 64)
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if err != nil {
return nil, exprErr{
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err: err,
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tok: t,
}
}
return Int{tok: tok(t), val: n}, nil
}
if t.Val == "true" {
return Bool{tok: tok(t), val: true}, nil
} else if t.Val == "false" {
return Bool{tok: tok(t), val: false}, nil
}
return Identifier{tok: tok(t), ident: t.Val}, nil
}
func parseString(t lexer.Token) (Expr, error) {
str, err := strconv.Unquote(t.Val)
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if err != nil {
return nil, exprErr{
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err: err,
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tok: t,
}
}
return String{tok: tok(t), str: str}, nil
}
func parseConnectingPunct(toks []lexer.Token, root Expr) (Expr, []lexer.Token, error) {
if toks[0].Equal(comma) {
return parseTuple(toks, root)
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} else if toks[0].Equal(pipe) {
return parsePipe(toks, root)
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} else if toks[0].Equal(arrow) {
expr, toks, err := parse(toks[1:])
if err != nil {
return nil, nil, err
}
pipe, ok := expr.(Pipe)
if !ok {
pipe = Pipe{exprs: []Expr{expr}}
}
return Statement{in: root, pipe: pipe}, toks, nil
}
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return root, toks, nil
}
func parseTuple(toks []lexer.Token, root Expr) (Expr, []lexer.Token, error) {
rootTup, ok := root.(Tuple)
if !ok {
rootTup = Tuple{exprs: []Expr{root}}
}
if len(toks) < 2 {
return rootTup, toks, nil
} else if !toks[0].Equal(comma) {
if toks[0].TokenType == lexer.Punctuation {
return parseConnectingPunct(toks, rootTup)
}
return rootTup, toks, nil
}
var expr Expr
var err error
if expr, toks, err = parseSingle(toks[1:]); err != nil {
return nil, nil, err
}
rootTup.exprs = append(rootTup.exprs, expr)
return parseTuple(toks, rootTup)
}
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func parsePipe(toks []lexer.Token, root Expr) (Expr, []lexer.Token, error) {
rootTup, ok := root.(Pipe)
if !ok {
rootTup = Pipe{exprs: []Expr{root}}
}
if len(toks) < 2 {
return rootTup, toks, nil
} else if !toks[0].Equal(pipe) {
if toks[0].TokenType == lexer.Punctuation {
return parseConnectingPunct(toks, rootTup)
}
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return rootTup, toks, nil
}
var expr Expr
var err error
if expr, toks, err = parseSingle(toks[1:]); err != nil {
return nil, nil, err
}
rootTup.exprs = append(rootTup.exprs, expr)
return parsePipe(toks, rootTup)
}
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// parseBlock assumes that the given token list is the entire block, already
// pulled from outer curly braces by sliceEnclosedToks, or determined to be the
// entire block in some other way.
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func parseBlock(toks []lexer.Token) (Block, error) {
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b := Block{}
var expr Expr
var err error
for {
if len(toks) == 0 {
return b, nil
}
if expr, toks, err = parse(toks); err != nil {
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return Block{}, err
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}
stmt, ok := expr.(Statement)
if !ok {
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return Block{}, exprErr{
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reason: "blocks may only contain full statements",
tok: expr.Token(),
tokCtx: "non-statement here",
}
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}
b.stmts = append(b.stmts, stmt)
}
}