conditional-statements

What is the difference between using: if (NULL == pointer) and using: if (pointer == NULL) My professor says to use the former over the latter but I don't see the difference between the two. Shafik Yaghmour There is no difference. What your professor prefers is called Yoda conditions also see "Yoda Conditions", "Pokémon Exception Handling" and other programming classics . It is supposed to prevent the usage of assignment( = ) by mistake over equality( == ) in a comparison, but modern compilers should warn about this now, so this type of defensive programming should not be needed. For example:

I'm currently using these sql statements. My table has the field CPaymentType which contains "Cash" or "Check". I can sum up the amount of payments by executing 2 SQL statements as shown below. In this case, the user won't even notice the speed difference when executing 2 sql statements or just 1, however, I don't like my way, I just want 1 sql statement. How do I reconstruct these into 1 statement with CASE conditions? I can't figure it out since examples online result in either 1 or 0 or boolean. I don't want the postdated Check payments to be included. Thank you very much. Select SUM

In C, one can do while( (i=a) != b ) { } but in Python, it appears, one cannot. while (i = sys.stdin.read(1)) != "\n": generates while (i = sys.stdin.read(1)) != "\n": ^ SyntaxError: invalid syntax (the ^ should be on the = ) Is there a workaround? Use break: while True: i = sys.stdin.read(1) if i == "\n": break # etc... You can accomplish this using the built-in function iter() using the two-argument call method: import functools for i in iter(fuctools.partial(sys.stdin.read, 1), '\n'): ... Documentation for this: iter(o[, sentinel]) ... If the second argument, sentinel , is given, then o

I would like to create a conditional task in Airflow as described in the schema below. The expected scenario is the following: Task 1 executes If Task 1 succeed, then execute Task 2a Else If Task 1 fails, then execute Task 2b Finally execute Task 3 All tasks above are SSHExecuteOperator. I'm guessing I should be using the ShortCircuitOperator and / or XCom to manage the condition but I am not clear on how to implement that. Could you please describe the solution? You have to use airflow trigger rules All operators have a trigger_rule argument which defines the rule by which the generated task

I want to write an if/else statement that tests if the value of a text input does NOT equal either one of two different values. Like this (excuse my pseudo-English code): var test = $("#test").val(); if (test does not equal A or B){ do stuff; } else { do other stuff; } How do I write the condition for the if statement on line 2? Think of ! (negation operator) as "not", || (boolean-or operator) as "or" and && (boolean-and operator) as "and". See Operators and Operator Precedence . Thus: if(!(a || b)) { // means neither a nor b } However, using De Morgan's Law , it could be written as: if(!a &&

I am try to make one function wait for another, and I would like to use NSCondionLock in order to accomplish this. I am not asking for help, but really hoping someone could show me a decent tutorial or example to explain NSConditionLock, or possibly suggest a better method. EDIT: as @Bonshington commented, this answer refers to NSCondition (as opposed to NSConditionLock ): - (void) method1 { [myCondition lock]; while (!someCheckIsTrue) [myCondition wait]; // Do something. [myCondition unlock]; } - (void) method2 { [myCondition lock]; // Do something. someCheckIsTrue = YES; [myCondition signal]