How to use the less/tree.functions function in less

eval: function (env) {
        var args = this.args.map(function (a) { return a.eval(env) });

        if (this.name in tree.functions) { // 1.
            return tree.functions[this.name].apply(tree.functions, args);
        } else { // 2.
            return new(tree.Anonymous)(this.name +
                   "(" + args.map(function (a) { return a.toCSS() }).join(', ') + ")");
        }
    },

eval: function (env) {
        var args = this.args.map(function (a) { return a.eval(env) });

        if (this.name in tree.functions) { // 1.
            return tree.functions[this.name].apply(tree.functions, args);
        } else { // 2.
            return new(tree.Anonymous)(this.name +
                   "(" + args.map(function (a) { return a.toCSS() }).join(', ') + ")");
        }
    },

eval: function (env) {
        var args = this.args.map(function (a) { return a.eval(env) });

        if (this.name in tree.functions) { // 1.
            return tree.functions[this.name].apply(tree.functions, args);
        } else { // 2.
            return new(tree.Anonymous)(this.name +
                   "(" + args.map(function (a) { return a.toCSS() }).join(', ') + ")");
        }
    },

eval: function (env) {
        var args = this.args.map(function (a) { return a.eval(env) });

        if (this.name in tree.functions) { // 1.
            return tree.functions[this.name].apply(tree.functions, args);
        } else { // 2.
            return new(tree.Anonymous)(this.name +
                   "(" + args.map(function (a) { return a.toCSS() }).join(', ') + ")");
        }
    },

eval: function (env) {
        var args = this.args.map(function (a) { return a.eval(env) });

        if (this.name in tree.functions) { // 1.
            return tree.functions[this.name].apply(tree.functions, args);
        } else { // 2.
            return new(tree.Anonymous)(this.name +
                   "(" + args.map(function (a) { return a.toCSS() }).join(', ') + ")");
        }
    },

property: function () {
                var name;

                if (name = $(/(\*?-?[-a-z_0-9]+)\s*:/g)) {
                    return name[1];
                }
            }
        }
    };
};

less.Parser.importer = null;

if (typeof(require) !== 'undefined') { var tree = require('less/tree') }

tree.functions = {
    rgb: function (r, g, b) {
        return this.rgba(r, g, b, 1.0);
    },
    rgba: function (r, g, b, a) {
        var rgb = [r, g, b].map(function (c) { return number(c) }),
            a = number(a);
        return new(tree.Color)(rgb, a);
    },
    hsl: function (h, s, l) {
        return this.hsla(h, s, l, 1.0);
    },
    hsla: function (h, s, l, a) {
        h = (((number(h) % 360) + 360) % 360) / 360;
        s = number(s); l = number(l); a = number(a);

        //require('sys').puts(h, s, l)

property: function () {
                var name;

                if (name = $(/(\*?-?[-a-z_0-9]+)\s*:/g)) {
                    return name[1];
                }
            }
        }
    };
};

less.Parser.importer = null;

if (typeof(require) !== 'undefined' && typeof(__LESS_DIST__) === 'undefined') { var tree = require('less/tree') }

tree.functions = {
    rgb: function (r, g, b) {
        return this.rgba(r, g, b, 1.0);
    },
    rgba: function (r, g, b, a) {
        var rgb = [r, g, b].map(function (c) { return number(c) }),
            a = number(a);
        return new(tree.Color)(rgb, a);
    },
    hsl: function (h, s, l) {
        return this.hsla(h, s, l, 1.0);
    },
    hsla: function (h, s, l, a) {
        h = (((number(h) % 360) + 360) % 360) / 360;
        s = number(s); l = number(l); a = number(a);

        //require('sys').puts(h, s, l)

property: function () {
                var name;

                if (name = $(/(\*?-?[-a-z_0-9]+)\s*:/g)) {
                    return name[1];
                }
            }
        }
    };
};

less.Parser.importer = null;

if (typeof(require) !== 'undefined' && typeof(__LESS_DIST__) === 'undefined') { var tree = require('less/tree') }

tree.functions = {
    rgb: function (r, g, b) {
        return this.rgba(r, g, b, 1.0);
    },
    rgba: function (r, g, b, a) {
        var rgb = [r, g, b].map(function (c) { return number(c) }),
            a = number(a);
        return new(tree.Color)(rgb, a);
    },
    hsl: function (h, s, l) {
        return this.hsla(h, s, l, 1.0);
    },
    hsla: function (h, s, l, a) {
        h = (((number(h) % 360) + 360) % 360) / 360;
        s = number(s); l = number(l); a = number(a);

        //require('sys').puts(h, s, l)