72 lines
1.8 KiB
JavaScript
72 lines
1.8 KiB
JavaScript
var ParseError = require("./ParseError");
|
|
|
|
// The main lexer class
|
|
function Lexer(input) {
|
|
this._input = input;
|
|
};
|
|
|
|
// The result of a single lex
|
|
function LexResult(type, text, position) {
|
|
this.type = type;
|
|
this.text = text;
|
|
this.position = position;
|
|
}
|
|
|
|
// "normal" types of tokens
|
|
var normals = [
|
|
[/^[/|@."`0-9]/, "textord"],
|
|
[/^[a-zA-Z]/, "mathord"],
|
|
[/^[*+-]/, "bin"],
|
|
[/^[=<>:]/, "rel"],
|
|
[/^[,;]/, "punct"],
|
|
[/^'/, "'"],
|
|
[/^\^/, "^"],
|
|
[/^_/, "_"],
|
|
[/^{/, "{"],
|
|
[/^}/, "}"],
|
|
[/^[(\[]/, "open"],
|
|
[/^[)\]?!]/, "close"]
|
|
];
|
|
|
|
// Build a regex to easily parse the functions
|
|
var anyFunc = /^\\(?:[a-zA-Z]+|.)/;
|
|
|
|
// Lex a single token
|
|
Lexer.prototype.lex = function(pos) {
|
|
var input = this._input.slice(pos);
|
|
|
|
// Get rid of whitespace
|
|
var whitespace = input.match(/^\s*/)[0];
|
|
pos += whitespace.length;
|
|
input = input.slice(whitespace.length);
|
|
|
|
// If there's no more input to parse, return an EOF token
|
|
if (input.length === 0) {
|
|
return new LexResult("EOF", null, pos);
|
|
}
|
|
|
|
var match;
|
|
if ((match = input.match(anyFunc))) {
|
|
// If we match one of the tokens, extract the type
|
|
return new LexResult(match[0], match[0], pos + match[0].length);
|
|
} else {
|
|
// Otherwise, we look through the normal token regexes and see if it's
|
|
// one of them.
|
|
for (var i = 0; i < normals.length; i++) {
|
|
var normal = normals[i];
|
|
|
|
if ((match = input.match(normal[0]))) {
|
|
// If it is, return it
|
|
return new LexResult(
|
|
normal[1], match[0], pos + match[0].length);
|
|
}
|
|
}
|
|
}
|
|
|
|
// We didn't match any of the tokens, so throw an error.
|
|
throw new ParseError("Unexpected character: '" + input[0] +
|
|
"' at position " + pos);
|
|
};
|
|
|
|
module.exports = Lexer;
|