An experiment in parentheses-free lisp (in JavaScript)
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import typ from "./representation.js";
import $ from "./tools.js";
import _ from "underscore";
import tokenizer from "./tokenize.js";
import desugarer from "./desugar.js";
import pprint from "./pprint.js";
import error from "./errors.js";
import closure from "./closures.js";
var print = console.log;
function sourcePos(tokens, linenum, charnum) {
if (!tokens || tokens.length === 0) {
return { linenum : linenum,
charnum : charnum
};
}
return {
linenum : fst(tokens)[3],
charnum : fst(tokens)[2]
};
}
function addSrcPos(stx, tokens, linenum, charnum) {
var pos = sourcePos(tokens, linenum, charnum);
stx.linenum = pos.linenum;
stx.charnum = pos.charnum;
return stx;
}
/* Gets the first token from the right side of the stack */
function fst(ts) {
return ts[ts.length-1];
}
/* Gets the second token from the right side of the stack */
function snd(ts) {
return ts[ts.length-2];
}
/*Checks if the next token is not followed by any of ``checks'' */
function notFollowedBy(tokens, checks, linenum, charnum) {
if (!fst(tokens)) {
throw error.JSyntaxError(0,0,"unexpected end of source");
}
var nextT = fst(tokens)[0];
if (checks.some(function (x) {
return x === nextT;
}))
return false;
else
return true;
}
/* returns a function that takes a parameter and
checks if it is in the array ``props''*/
function makeChecker(props) {
return function(x) {
return x && props.some(function (y) {return y(x);});
};
}
function tokTypeCheck(name) {
return function(tok) {
return tok[0] === name;
};
}
function formTypeCheck(stxtype) {
return function(stx) {
return stx.exprType === stxtype;
};
}
/*Tries to parse until the prediction ``valid'' fails or the wrong type is parsed
Collects the results into an array and returns it*/
function parseMany(parse, exprType, valid, tokens, charnum, linenum) {
if (!fst(tokens)) {
throw error.JSyntaxError(charnum,
linenum,
"Unexpected end of source");
}
var current = fst(tokens)[0];
var results = [];
var parsed;
if (valid(fst(tokens))) {
parsed = parse(tokens);
}
else {
throw error.JSyntaxError(fst(tokens)[3],
fst(tokens)[2],
"Unexpected token: ``"+fst(tokens)[0]+"''");
}
results.push(parsed);
//make sure there are at least 2 tokens to parse
if (tokens.length > 1 && fst(tokens) && valid(fst(tokens))) {
while (valid(snd(tokens))) {
if (!(valid(fst(tokens)))) {
break;
}
results.push(parse(tokens));
if (!exprType(fst(results).exprType)) {
break;
}
if (fst(tokens)) {
current = fst(tokens)[0];
}
else {
throw error.JSyntaxError(linenum,
charnum,
"Unexpected end of source");
}
if (tokens.length <= 1) {
break;
}
}
}
//do the same validity check as before and in the loop
if (!fst(tokens)) {
throw error.JSyntaxError(fst(tokens)[3],
fst(tokens)[2],
"unexpected end of source");
}
if (valid(fst(tokens))) {
results.push(parse(tokens));
}
return results;
}
/* Tries to parse exprType separated by the token between
* e.g. <identifier>,<identifier>,...
*/
function parseBetween(exprType, between, tokens, charnum, linenum) {
var first = parse(tokens);
var items;
var parsed;
if (!exprType(first)) {
throw error.JSyntaxError(fst(tokens)[2], fst(tokens)[3], "Unexpected token: ``"+fst(tokens)[0]+"''");
}
items = [first];
if (tokens.length > 1 && fst(tokens)[0] === between) {
while (fst(tokens)[0] === between) {
tokens.pop();
parsed = parse(tokens);
if (!fst(tokens))
throw error.JSyntaxError(fst(tokens)[3],
fst(tokens)[2],
"Missing terminator: "+between);
items.push(parsed);
}
return items;
}
return items;
}
function parseList(tokens, linenum, charnum) {
var xs;
var result;
if (fst(tokens)[0] === "right_square") {
xs = [];
}
else if (fst(tokens)[0] === "comma") {
tokens.pop();
xs = [];
}
else {
xs = parseBetween(function (x) {
return true;
}, "comma", tokens, fst(tokens)[3], fst(tokens)[2]);
}
if (!fst(tokens) || fst(tokens)[0] !== "right_square") {
throw error.JSyntaxError(fst(tokens)[3],
fst(tokens)[2],
"list must be terminated by ]");
}
tokens.pop();
result = addSrcPos(new typ.ListT(xs), tokens, linenum, charnum);
return result;
}
function parseDefFunction(tokens, linenum, charnum) {
var fname = parse(tokens);
var parameters;
var result;
var body;
if (fname.exprType !== "Name") {
throw error.JSyntaxError(linenum,
charnum,
"Expected an identifier in function definition");
}
if (fst(tokens)[0] === "right_paren") {
parameters = [];
}
else {
parameters = parseMany(parse,
validName,
validFormPar,
tokens,
charnum,
linenum);
}
if (!tokens || (fst(tokens)[0]) !== "right_paren") {
throw error.JSyntaxError(linenum,
charnum,
"Formal parameters must be followed by )");
}
tokens.pop();
body = parse(tokens);
result = addSrcPos(new typ.DefFunc(fname, parameters, body), tokens, body.linenum, body.charnum);
return result;
}
var validLet = makeChecker(["Definition", "FunctionDefinition"].map(formTypeCheck));
var letEnd = _.compose($.not, makeChecker(["right_brace"].map(tokTypeCheck)));
function parseLetForm(tokens, linenum, charnum) {
var result;
var pairs;
var body;
if (!fst(tokens)) {
error.JSyntaxError(linenum,
charnum,
"Unexpected end of source");
}
pairs = parseMany(parseLetItem,
validLet,
letEnd,
tokens,
charnum,
linenum);
if (fst(tokens) && fst(tokens)[0] !== "right_brace") {
throw error.JSyntaxError(fst(tokens)[2],
fst(tokens)[3],
"let/def form must have a closing }");
}
if (!fst(tokens)) {
throw error.JSyntaxError(_.last(pairs).linenum,
_.last(pairs).charnum,
"Unexpected end of source");
}
tokens.pop();
if (tokens.length <= 0) {
throw error.JSyntaxError(_.last(pairs).linenum,
_.last(pairs).charnum,
"let/def form must have a body");
}
body = parse(tokens);
if (body.exprType === "Definition" ||
body.exprType === "FunctionDefinition") {
throw error.JSyntaxError(body.linenum,
body.charnum,
"Body of a let/def expression cannot be a definition");
}
result = addSrcPos(new typ.LetExp(pairs, body), tokens, body.linenum, body.charnum);
return result;
}
function parseLetFunction(tokens, linenum, charnum) {
var fname = parse(tokens);
var parameters;
var result;
var body;
if (fname.exprType != "Name") {
throw error.JSyntaxError(fst(tokens)[3],
fst(tokens)[2],
"Expected an identifier in function definition");
}
if (fst(tokens)[0] === "right_paren") {
parameters = [];
}
else {
parameters = parseMany(parse,
validName,
validFormPar,
tokens,
charnum,
linenum);
}
if ((fst(tokens)[0]) !== "right_paren") {
throw error.JSyntaxError(linenum,
charnum,
"Formal parameters must be followed by )");
}
tokens.pop();
if (fst(tokens)[1] !== "->") {
throw error.JSyntaxError(fst(tokens)[3],
fst(tokens)[2],
"Function parameters in let/def form must be followed by ->");
}
tokens.pop();
body = parse(tokens);
result = addSrcPos(new typ.DefFunc(fname, parameters, body), tokens, body.linenum, body.charnum);
return result;
}
function parseLetBinding(tokens, linenum, charnum) {
var name = parse(tokens);
var result;
var bound;
if (name.exprType != "Name") {
throw error.JSyntaxError(name.linenum,
name.charnum,
"Expected an identifier in let/def binding");
}
if (!fst(tokens) || fst(tokens)[1] !== "=") {
throw error.JSyntaxError(name.linenum,
name.charnum,
"An identifier in a let/def binding must be followed by ``=''");
}
tokens.pop();
if (!notFollowedBy(tokens,
["comma", "arrow", "right_brace", "right_square"],
name.linenum,
name.charnum)) {
throw error.JSyntaxError(name.linenum,
name.charnum,
"The binding of " + identifier.val + " must not be followed by " + fst(tokens)[0]);
}
bound = parse(tokens);
if (bound.exprType === "Definition" ||
bound.exprType === "FunctionDefinition") {
throw error.JSyntaxError(bound.linenum,
bound.charnum,
"A definition cannot be the value of a binding");
}
result = addSrcPos(new typ.Def(name, bound), tokens, bound.linenum, bound.charnum);
return result;
}
function parseLetItem(tokens) {
var linenum = fst(tokens)[3];
var charnum = fst(tokens)[2];
if (fst(tokens) && fst(tokens)[0] === "left_paren") {
tokens.pop();
return parseLetFunction(tokens,
linenum,
charnum);
}
else {
return parseLetBinding(tokens,
linenum,
charnum);
}
}
function parseDataType(tokens, linenum, charnum) {
var typeName = parse(tokens, linenum, charnum);
var typeParams;
var typeBody;
var result;
if (typeName.exprType !== "TypeOperator") {
throw error.JSyntaxError(typeName.linenum,
typeName.charnum,
"Expected a type operator in data type definition");
}
if (fst(tokens)[0] !== "right_paren") {
var parameters = parseMany(parse,
validName,
validFormPar,
tokens,
charnum,
linenum);
}
else {
var parameters = [];
}
if (!tokens || (fst(tokens)[0]) !== "right_paren") {
throw error.JSyntaxError(_.last(parameters).linenum,
_.last(parameters).charnum,
"Data type parameters must be followed by )");
}
tokens.pop();
typeBody = parse(tokens);
result = addSrcPos(new typ.DataType(typeName, parameters, typeBody), tokens, typeBody.linenum, typeBody.charnum);
return result;
}
function parseDefType(tokens, linenum, charnum) {
var result;
var rhs;
var lhs;
if (tokens.length < 2) {
/* Minimal number of tokens required is 2
* because it could be 'deftype Foo Blah'
*/
throw error.JSyntaxError(linenum,
charnum,
"Unexpected end of source");
}
if (fst(tokens)[0] === "left_paren") {
/* It's an actual data type definition
* i.e. not just an alias
*/
tokens.pop();
return parseDataType(tokens, linenum, charnum);
}
if (notFollowedBy(tokens, ["constructor"], linenum, charnum)) {
throw error.JSyntaxError(linenum,
charnum,
"deftype must be followed by a single constructor" +
" if it is not a data type definition with type variables");
}
else {
lhs = parse(tokens, linenum, charnum);
if (!tokens) {
throw error.JSyntaxError(lhs.linenum,
lhs.charnum,
"Unexpected end of source");
}
if (lhs.exprType !== "TypeOperator") {
throw error.JSyntaxError(lhs.linenum,
lhs.charnum,
"left-hand side of type alias was not a type operator");
}
rhs = parse(tokens, linenum, charnum);
if (rhs.exprType !== "Application" &&
rhs.exprType !== "TypeOperator") {
throw error.JSyntaxError(rhs.linenum,
rhs.charnum,
"was expecting an application or type operator on the right-hand side of a type alias");
}
result = addSrcPos(new typ.DefType(lhs, rhs), tokens, rhs.linenum, rhs.charnum);
return result;
}
}
function parseDef(tokens, linenum, charnum) {
var result;
var identifier;
var bound;
if (tokens.length < 2) {
/* Minimal number of tokens required is 2
* because it could be 'def foo blah'
*/
throw error.JSyntaxError(linenum,
charnum,
"Unexpected end of source");
}
if (fst(tokens)[0] === "left_paren") {
/* It's a function definition */
tokens.pop();
return parseDefFunction(tokens, linenum, charnum);
}
if (fst(tokens)[0] === "left_brace") {
/* It's a let/def form */
tokens.pop();
return parseLetForm(tokens,
fst(tokens)[3],
fst(tokens)[2]);
}
if (notFollowedBy(tokens, ["identifier"], linenum, charnum)) {
throw error.JSyntaxError(linenum,
charnum,
"def must be followed by identifier, not "+fst(tokens)[0]);
}
else {
identifier = parse(tokens);
if (!fst(tokens))
throw error.JSyntaxError(identifier.linenum,
identifier.charnum,
"Unexpected end of source");
if (!notFollowedBy(tokens,
["comma", "arrow", "right_brace", "right_square"],
identifier.linenum,
identifier.charnum)) {
throw error.JSyntaxError(identifier.linenum,
identifier.charnum,
"def " + identifier.val + " must not be followed by " + fst(tokens)[0]);
}
bound = parse(tokens);
if (bound.exprType === "Definition" ||
bound.exprType === "FunctionDefinition") {
throw error.JSyntaxError(bound.linenum,
bound.charnum,
"A definition cannot be the value of a binding");
}
result = addSrcPos(new typ.Def(identifier, bound), tokens, bound.linenum, bound.charnum);
return result;
}
}
function parseDefOp(tokens, linenum, charnum) {
var result;
var names;
var pattern;
if (fst(tokens)[0] !== "integer" ||
fst(tokens)[1] < 1) {
throw error.JSyntaxError(linenum,
charnum,
"defop must be followed by integer precedence >= 1");
}
tokens.pop();
if (fst(tokens)[1] !== "Left" && fst(tokens)[1] !== "Right") {
throw error.JSyntaxError(linenum,
charnum,
"defop must be followed by precedence and then either Left or Right");
}
tokens.pop();
if (fst(tokens)[0] !== "left_paren") {
throw error.JSyntaxError(linenum,
charnum,
"defop arguments must start with (");
}
tokens.pop();
if (!(tokens.slice(tokens.length-3,
tokens.length).every(function(x) {
return x[0] === "identifier";
}))) {
throw error.JSyntaxError(linenum,
charnum,
"defop must be surrounded by exactly 3 identifiers");
}
pattern = tokens.slice(tokens.length-3,
tokens.length);
tokens.pop(); tokens.pop(); tokens.pop();
if (fst(tokens)[0] !== "right_paren") {
throw error.JSyntaxError(linenum,
charnum,
"defop pattern must be terminated with )");
}
tokens.pop();
names = [new typ.Name(pattern[1][1]),
new typ.Name(pattern[0][1]),
new typ.Name(pattern[2][1])];
names.map(function(name) {
name.linenum = linenum;
name.charnum = charnum;
return name;
});
result = addSrcPos(new typ.DefFunc(names[0],
names.slice(1,3),
parse(tokens)),
tokens,
_.last(names).linenum,
_.last(names).charnum);
return result;
}
function parseIf(tokens, linenum, charnum) {
var result;
var ifC;
var thenC;
var elseC;
if (!notFollowedBy(tokens,
["def","comma","lambda"],
linenum,
charnum)) {
throw error.JSyntaxError(linenum,
charnum,
"``if'' cannot be followed by "+fst(tokens)[0]) ;
}
else {
ifC = parse(tokens);
if (!fst(tokens) || fst(tokens)[0] !== "thenexp") {
throw error.JSyntaxError(ifC.linenum,
ifC.charnum,
"if ``exp'' must be folowed by ``then'' exp, not "+snd(tokens)[0]);
}
else {
tokens.pop();
thenC = parse(tokens);
if (fst(tokens) && fst(tokens)[0] === "elsexp") {
tokens.pop();
if (_.size(tokens) < 1) {
throw error.JSyntaxError(thenC.linenum,
thenC.charnum,
"Unexpected end of source");
}
else {
elseC = parse(tokens);
result = addSrcPos(new typ.If(ifC, thenC, elseC), tokens, elseC.linenum, elseC.charnum);
return result;
}
}
else {
throw error.JSyntaxError(thenC.linenum,
thenC.charnum,
"If expression must include an else variant");
}
}
}
}
var validName = makeChecker(["Name"].map(formTypeCheck));
function validFormPar(tok) {
return tok[0] === "identifier" &&
tok[1] !== "->";
}
function parseLambda(tokens, linenum, charnum) {
var result;
var parameters = parseMany(parse,
validName,
validFormPar,
tokens,
charnum,
linenum);
if (fst(tokens)[1] !== "->") {
throw error.JSyntaxError(_.last(parameters).linenum,
_.last(parameters).charnum,
"arrow must follow parameters in lambda, not "+fst(tokens)[0]);
}
tokens.pop();
var body = parse(tokens);
result = addSrcPos(new typ.FuncT(parameters, body), tokens, body.linenum, body.charnum);
return result;
}
var invalidArguments = ["def", "comma", "right_paren", "right_square", "right_brace", "left_brace", "right_brace"].map(tokTypeCheck);
var validArgument = _.compose($.not, makeChecker(invalidArguments));
var validArgTypes = _.compose($.not, makeChecker(["Definition"].map(formTypeCheck)));
/* Parses function application (either infix or prefix) */
function computeApp(tokens, charnum, linenum) {
var lhs = parse(tokens);
var next;
var result;
var parameters;
if (fst(tokens)) {
next = fst(tokens);
}
else {
throw error.JSyntaxError(lhs.linenum,
lhs.charnum,
"Unexpected end of source");
}
if (typ.OPInfo[next[1]]) {
/* it's an infix expression */
result = parseInfix(tokens, 1, lhs, lhs.linenum, lhs.charnum);
if (!fst(tokens) || fst(tokens)[0] !== "right_paren") {
throw error.JSyntaxError(lhs.linenum,
lhs.charnum,
"Mismatched parentheses or missing parenthesis on right-hand side");
}
else {
tokens.pop();
return result;
}
}
else {
/* it's a prefix application */
if (fst(tokens)[0] !== "right_paren") {
parameters = parseMany(parse,
validArgTypes,
validArgument,
tokens,
fst(tokens)[2],
fst(tokens)[3]);
}
else {
parameters = [];
}
if ((!fst(tokens)) || fst(tokens)[0] !== "right_paren") {
throw error.JSyntaxError(fst(tokens)[3],
fst(tokens)[2],
"Mismatched parentheses or missing parenthesis on right-hand side");
}
else {
tokens.pop();
return addSrcPos(typ.makeApp(lhs, parameters), tokens, linenum, charnum);
}
}
}
/*Parses infix expressions by precedence climbing
* console.log(stx);
See this for more info and an implementation in python
http://eli.thegreenplace.net/2012/08/02/parsing-expressions-by-precedence-climbing/
*/
function parseInfix(tokens, minPrec, lhs, linenum, charnum) {
if (!lhs) {
lhs = parse(tokens);
}
while (true) {
var cur = fst(tokens);
if (!cur) {
throw error.JSyntaxError(linenum,
charnum,
"Unexpected end of source");
}
var opinfo = typ.OPInfo[cur[1]];
if (!opinfo || opinfo[0] < minPrec)
break;
var op = addSrcPos(new typ.Name(cur[1]), tokens, linenum, charnum);
var prec = opinfo[0];
var assoc = opinfo[1];
var nextMinPrec = assoc === "Left" ? prec + 1 : prec;
tokens.pop();
/*remove the operator token*/
var rhs = parseInfix(tokens, nextMinPrec);
lhs = addSrcPos(typ.makeApp(op, [lhs, rhs]), tokens, rhs.linenum, rhs.charnum);
}
return lhs;
}
function parse(tokens) {
var charnum = fst(tokens)[2];
var linenum = fst(tokens)[3];
var toktype;
var result;
if (fst(tokens)) {
toktype = fst(tokens)[0];
}
else {
console.error("Tokenization error");
}
var token = fst(tokens)[1];
tokens.pop();
if (toktype === "stringlit") {
result = addSrcPos(new typ.StrT(token), tokens, linenum, charnum);
return result;
}
else if (toktype === "left_square") {
return parseList(tokens, linenum, charnum);
}
else if (toktype === "lambda") {
return parseLambda(tokens, linenum, charnum);
}
else if (toktype === "integer") {
result = addSrcPos(new typ.IntT(token), tokens, linenum, charnum);
return result;
}
else if (toktype === "float") {
result = addSrcPos(new typ.FloatT(token), tokens, linenum, charnum);
return result;
}
else if (toktype === "identifier") {
result = addSrcPos(new typ.Name(token), tokens, linenum, charnum);
return result;
}
else if (toktype === "constructor") {
result = addSrcPos(new typ.TypeOp(token), tokens, linenum, charnum);
return result;
}
else if (toktype === "truelit" || toktype === "falselit") {
result = addSrcPos(new typ.BoolT(token), tokens, linenum, charnum);
return result;
}
else if (toktype === "def" ||
toktype === "let") {
return parseDef(tokens, linenum, charnum);
}
else if (toktype === "deftype") {
return parseDefType(tokens, linenum, charnum);
}
else if (toktype === "defop") {
return parseDefOp(tokens, linenum, charnum);
}
else if (toktype === "ifexp") {
return parseIf(tokens, linenum, charnum);
}
else if (toktype === "left_paren") {
if (tokens.length == 0) {
throw error.JSyntaxError(linenum,
charnum,
"Unexpected end of source");
}
if (fst(tokens)[0] === "lambda") {
tokens.pop();
var parsed = parseLambda(tokens, linenum, charnum);
tokens.pop();
return parsed;
}
else
return computeApp(tokens, linenum, charnum);
}
else {
throw error.JSyntaxError(linenum,
charnum,
"Unexpected token: ``" + toktype+"''");
}
}
function parseFull(tokenized) {
var ast = [];
var typeBindings = {};
var current;
while (tokenized.length > 0) {
current = closure.annotate_fvs(desugarer.desugar(parse(tokenized), typeBindings));
ast.push(current);
}
return {
"ast" : ast,
"types" : typeBindings
};
}
export default { parse : function(str) {
return parseFull(tokenizer.tokenize(str));
},
tokenize : tokenizer.tokenize,
parseFull : parseFull,
};
//var testParse = parseFull(tokenizer.tokenize(istr));
//console.log(testParse[1]);
//console.log(testParse[0].map(pprint.pprint));