Function operation

tools/pythonauto/static/codemirrorepl/codemirrorepl.js:2094–2101

(f)

        }
        var nestedOperation = 0;
        function operation(f) {
            return function() {
                if (!nestedOperation++) startOperation();
                try {var result = f.apply(this, arguments);}
                finally {if (!--nestedOperation) endOperation();}
                return result;
            };
        }

        function compoundChange(f) {
            history.startCompound();