An experiment in parentheses-free lisp (in JavaScript)
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function compose(f, g) {
return function(x) {
return f(g(x));
};
}
function not(x) {
return !x;
}
function on(g, f) {
return function(x,y) {
return g(f(x), f(y));
};
}
function max(f, a, b) {
if (f(a) >= f(b))
return a;
return b;
}
function maxBy(f, xs) {
if (xs.length < 1)
return false;
return xs.reduce(function(maxval, a) { return max(f, maxval, a); });
}
function len(xs) {
return xs.length;
}
function takeWhile(f, xs) {
var result = [];
for (i = 0; i < xs.length; i++) {
if (f(xs[i]))
result.push(xs[i]);
else
break;
}
return result;
}
function dropWhile(f, xs) {
for (i = 0; i < xs.length; i++) {
if (!f(xs[i]))
break;
}
return xs.slice(i);
}
function span(f, xs) {
return [takeWhile(f, xs), dropWhile(f, xs)];
}
function eq(a) {
return function(b) {
return a[0] === b[0];
};
}
function groupBy(eq, xs) {
var groups = [];
var spanned;
while (xs.length > 0) {
spanned = span(eq(xs[0]), xs.slice(1));
groups.push([xs[0]].concat(spanned[0]));
xs = spanned[1];
}
return groups;
}
function groupOps(ops) {
return groupBy(eq, ops.sort());
}
// See: https://en.wikipedia.org/wiki/Trie
function buildTrie(prefix, operators) {
var grps = groupOps(operators);
return [prefix, grps.map(
function(ops) {
if (ops.length === 1)
return ops;
return buildTrie(ops[0][0],
ops.map(
function(op) {
return op.slice(1);
}).filter(function (x){ return x;}));
})];
}
function matchStr(n, str, trie) {
if (trie[0][0].length > 1 && str.length <= 1)
return false;
else if (trie[0].every(function(x){return x[0][0] !== str[0];})) {
return false;
}
else if (trie[0].length === 1) {
if (trie[0][0] !== str.slice(n, trie[0][0].length))
return false;
return trie[0][0].length + n;
}
else {
return matchStr(n+1, str.slice(1), trie[0][1])
}
}
console.log(matchStr(0, "**^*$4545", buildTrie("", ["**", "**^"])[1]));
module.exports = {compose : compose,
not : not,
on : on,
maxBy : maxBy,
len : len,
groupOps : groupOps,
buildTrie : buildTrie}