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test.html
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test.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
</head>
<body>
<script>
function InputStream(input) {
var pos = 0,
line = 1,
col = 0;
return {
next: next,
peek: peek,
eof: eof,
croak: croak,
};
function next() {
var ch = input.charAt(pos++);
if (ch == '\n') line++, (col = 0);
else col++;
return ch;
}
function peek() {
return input.charAt(pos);
}
function eof() {
return peek() == '';
}
function croak(msg) {
throw new Error(msg + ' (' + line + ':' + col + ')');
}
}
function TokenStream(input) {
var current = null;
var keywords = ' if then else lambda λ true false ';
return {
next: next,
peek: peek,
eof: eof,
croak: input.croak,
};
function is_keyword(x) {
return keywords.indexOf(' ' + x + ' ') >= 0;
}
function is_digit(ch) {
return /[0-9]/i.test(ch);
}
function is_id_start(ch) {
return /[a-zλ_]/i.test(ch);
}
function is_id(ch) {
return is_id_start(ch) || '?!-<>=0123456789'.indexOf(ch) >= 0;
}
function is_op_char(ch) {
return '+-*/%=&|<>!'.indexOf(ch) >= 0;
}
function is_punc(ch) {
return ',;(){}[]'.indexOf(ch) >= 0;
}
function is_whitespace(ch) {
return ' \t\n'.indexOf(ch) >= 0;
}
function read_while(predicate) {
var str = '';
while (!input.eof() && predicate(input.peek())) str += input.next();
return str;
}
function read_number() {
var has_dot = false;
var number = read_while(function (ch) {
if (ch == '.') {
if (has_dot) return false;
has_dot = true;
return true;
}
return is_digit(ch);
});
return { type: 'num', value: parseFloat(number) };
}
function read_ident() {
var id = read_while(is_id);
return {
type: is_keyword(id) ? 'kw' : 'var',
value: id,
};
}
function read_escaped(end) {
var escaped = false,
str = '';
input.next();
while (!input.eof()) {
var ch = input.next();
if (escaped) {
str += ch;
escaped = false;
} else if (ch == '\\') {
escaped = true;
} else if (ch == end) {
break;
} else {
str += ch;
}
}
return str;
}
function read_string() {
return { type: 'str', value: read_escaped('"') };
}
function skip_comment() {
read_while(function (ch) {
return ch != '\n';
});
input.next();
}
function read_next() {
read_while(is_whitespace);
if (input.eof()) return null;
var ch = input.peek();
if (ch == '#') {
skip_comment();
return read_next();
}
if (ch == '"') return read_string();
if (is_digit(ch)) return read_number();
if (is_id_start(ch)) return read_ident();
if (is_punc(ch))
return {
type: 'punc',
value: input.next(),
};
if (is_op_char(ch))
return {
type: 'op',
value: read_while(is_op_char),
};
input.croak("Can't handle character: " + ch);
}
function peek() {
return current || (current = read_next());
}
function next() {
var tok = current;
current = null;
return tok || read_next();
}
function eof() {
return peek() == null;
}
}
var FALSE = { type: 'bool', value: false };
function parse(input) {
var PRECEDENCE = {
'=': 1,
'||': 2,
'&&': 3,
'<': 7,
'>': 7,
'<=': 7,
'>=': 7,
'==': 7,
'!=': 7,
'+': 10,
'-': 10,
'*': 20,
'/': 20,
'%': 20,
};
return parse_toplevel();
function is_punc(ch) {
var tok = input.peek();
return tok && tok.type == 'punc' && (!ch || tok.value == ch) && tok;
}
function is_kw(kw) {
var tok = input.peek();
return tok && tok.type == 'kw' && (!kw || tok.value == kw) && tok;
}
function is_op(op) {
var tok = input.peek();
return tok && tok.type == 'op' && (!op || tok.value == op) && tok;
}
function skip_punc(ch) {
if (is_punc(ch)) input.next();
else input.croak('Expecting punctuation: "' + ch + '"');
}
function skip_kw(kw) {
if (is_kw(kw)) input.next();
else input.croak('Expecting keyword: "' + kw + '"');
}
function skip_op(op) {
if (is_op(op)) input.next();
else input.croak('Expecting operator: "' + op + '"');
}
function unexpected() {
input.croak('Unexpected token: ' + JSON.stringify(input.peek()));
}
// 从左到右遍历，按符号优先级进行包装，下一个运算符比上一个binary结构的运算符大的话，对后面的进行包装新的bianry（因为解析执行时按深度优先遍历，所以会先执行，从而满足高优先级的运算符先执行）
function maybe_binary(left, my_prec) {
var tok = is_op();
if (tok) {
var his_prec = PRECEDENCE[tok.value];
if (his_prec > my_prec) {
input.next();
const right = maybe_binary(parse_atom(), his_prec);
return maybe_binary(
{
type: tok.value == '=' ? 'assign' : 'binary',
operator: tok.value,
left: left,
right: right,
},
my_prec
);
}
}
return left;
}
function delimited(start, stop, separator, parser) {
var a = [],
first = true;
skip_punc(start);
while (!input.eof()) {
if (is_punc(stop)) break;
if (first) first = false;
else skip_punc(separator);
if (is_punc(stop)) break;
a.push(parser());
}
skip_punc(stop);
return a;
}
function parse_call(func) {
return {
type: 'call',
func: func,
args: delimited('(', ')', ',', parse_expression),
};
}
function parse_varname() {
var name = input.next();
if (name.type != 'var') input.croak('Expecting variable name');
return name.value;
}
function parse_if() {
skip_kw('if');
var cond = parse_expression();
if (!is_punc('{')) skip_kw('then');
var then = parse_expression();
var ret = {
type: 'if',
cond: cond,
then: then,
};
if (is_kw('else')) {
input.next();
ret.else = parse_expression();
}
return ret;
}
function parse_lambda() {
return {
type: 'lambda',
vars: delimited('(', ')', ',', parse_varname),
body: parse_expression(),
};
}
function parse_bool() {
return {
type: 'bool',
value: input.next().value == 'true',
};
}
function maybe_call(expr) {
expr = expr();
return is_punc('(') ? parse_call(expr) : expr;
}
function parse_atom() {
return maybe_call(function () {
if (is_punc('(')) {
input.next();
var exp = parse_expression();
skip_punc(')');
return exp;
}
if (is_punc('{')) return parse_prog();
if (is_kw('if')) return parse_if();
if (is_kw('true') || is_kw('false')) return parse_bool();
if (is_kw('lambda') || is_kw('λ')) {
input.next();
return parse_lambda();
}
var tok = input.next();
if (tok.type == 'var' || tok.type == 'num' || tok.type == 'str')
return tok;
unexpected();
});
}
function parse_toplevel() {
var prog = [];
while (!input.eof()) {
prog.push(parse_expression());
if (!input.eof()) skip_punc(';');
}
return { type: 'prog', prog: prog };
}
function parse_prog() {
var prog = delimited('{', '}', ';', parse_expression);
if (prog.length == 0) return FALSE;
if (prog.length == 1) return prog[0];
return { type: 'prog', prog: prog };
}
function parse_expression() {
return maybe_call(function () {
return maybe_binary(parse_atom(), 0);
});
}
}
</script>
</body>
</html>