An experiment in parentheses-free lisp (in JavaScript)
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#! /usr/bin/node
var fs = require("fs");
function isDigit(a) {
if (!a)
return false;
var code = a.charCodeAt();
return (46 < code && code < 58 || code < 58 && code > 46);
}
function isWhitespace(a) {
if (!a)
return true;
var code = a.charCodeAt();
return (code === 9 || code === 32 || code === 10 || code === 13 || code === 11);
}
function tokenizeNum() {
var number = [];
var code = tokstream[0].charCodeAt();
var isFloat = false;
// + -
if (code === 43 || code === 45) {
number.push(tokstream[0]);
tokstream = tokstream.substr(1);
}
else if (code === 46) {
tokstream = tokstream.substr(1);
number.push('0');
number.push('.');
isFloat = true;
}
while (isDigit(tokstream[0]) && tokstream.length !== 0) {
number.push(tokstream[0]);
tokstream = tokstream.substr(1);
}
if (tokstream[0] === '.' && isDigit(tokstream[1])) {
number.push('.');
number.push(tokstream[1]);
tokstream = tokstream.substr(2);
while (isDigit(tokstream[0]) && tokstream.length !== 0) {
number.push(tokstream[0]);
tokstream = tokstream.substr(1);
}
return ["Float", parseFloat(number.join(''), 10)];
}
if (!isFloat)
return ["Integer", parseInt(number.join(''), 10)];
else
return ["Float", parseFloat(number.join(''), 10)];
}
function tokenizeIdent() {
var identifier = [];
while (!isWhitespace(tokstream[0])) {
identifier.push(tokstream[0]);
tokstream = tokstream.substr(1);
}
return ["identifier", identifier.join('')];
}
function tokenize() {
var tokens = [];
while (tokstream) {
switch (tokstream[0].charCodeAt()) {
case 9: // '\t'
tokens.push(["whitespace", '\t']);
tokstream = tokstream.substr(1);
break;
case 32: // ' '
tokens.push(["whitespace", ' ']);
tokstream = tokstream.substr(1);
break;
case 10: // '\n'
tokens.push(["whitespace", '\n']);
tokstream = tokstream.substr(1);
break;
case 40: // '('
tokens.push(["left_paren", '(']);
tokstream = tokstream.substr(1);
break;
case 41: // ')'
tokens.push(["right_paren", ')']);
tokstream = tokstream.substr(1);
break;
case 123: // '{'
tokens.push(["left_brace", '{']);
tokstream = tokstream.substr(1);
break;
case 125: // '}'
tokens.push(["right_brace", '}']);
tokstream = tokstream.substr(1);
break;
case 91: // '['
tokens.push(["left_square", '[']);
tokstream = tokstream.substr(1);
break;
case 93: // ']'
tokens.push(["right_square", ']']);
tokstream = tokstream.substr(1);
break;
case 43: // '+'
var num = tokenizeNum();
if (num !== NaN)
tokens.push(num);
break;
case 45: // '-'
var num = tokenizeNum();
if (num !== NaN)
tokens.push(num);
break;
case 46: // '.'
var num = tokenizeNum();
if (num !== NaN)
tokens.push(num);
break;
default:
if (isDigit(tokstream[0])) {
var num = tokenizeNum();
if (num !== NaN)
tokens.push(num);
break;
}
var ident = tokenizeIdent();
tokens.push(ident);
}
}
return tokens;
}
//var input = process.argv.slice(2).reduce(function(acc, x) {return acc + " " + x}, "").trim();
var tokstream = fs.readFileSync("/dev/stdin").toString();
console.log(tokenize());