Results

function guard(fn, g) {
    return function(x) {
        return g(x) ? fn(x) : undefined;
    }
}
function callIfPositive(fn) {
    return guard(fn, function(x) { return x > 0; });
}
var logIfPositive = callIfPositive(log);
for (var i = -5; i < 5; i++)
    logIfPositive(i);