gistfile1.js

// And then...
var square = c.func({
    'input': function () {
        this.assert( arguments.length == 1, Error("Wrong number of arguments" ) );
        this.assert( typeof arguments[0] == 'number', Error('Argument is a number') );
    },
    'output': function () {
        this.assert( typeof arguments[0] == 'number', Error('Output is a number') );
    },
    'body': function (target) {
        return target * target;
    }
});