(This is a generalization of your idea for two arrays.) If you start by looking at the five medians of the five arrays, obviously the overall median must be between the smallest and the largest of the five medians. Proof goes something like this: If a is the min of the medians, and b is … Read more
For a simple calculator with only 5 operators (^, *, /, +, -) and no parentheses, you can do something like this. First, it is convenient to turn the string into an array of numbers and operators. Then, we go through the array looking for each operator in order of precedence, and applying the operator … Read more
you could use the modulus operator for(int i = 0; i < 500; i++) { if(i % 5 == 0) { //do your stuff here } }
To do conditional write operations you need to use the FOREACH trick. Using CASE you either return a one element array or a empty one. FOREACH iterates over the CASE expression and therefore conditionally executes the action. If you want an ELSE part as well you need to have a another FOREACH using the inverse … Read more
If my driveway is empty, I cannot assert that all cars parked there are red. Consider the following statements. S1: My driveway is empty. S2: All the cars parked in my driveway are red. I claim that S1 implies S2. That is, the statement S1 => S2 is true. I will do this by showing … Read more
Essentially, Coq has both because they are useful for different things: booleans correspond to facts that can be checked mechanically (i.e., with an algorithm), whereas propositions can express more concepts. Strictly speaking, the logical and boolean worlds are not separate in Coq: the boolean world is a subset of the logical world. In other words, … Read more
PHP’s comparison operators deviate from the computer-scientific definitions in several ways: In order to constitute an equivalence relation == has to be reflexive, symmetric and transitive: PHP’s == operator is not reflexive, i.e. $a == $a is not always true: var_dump(NAN == NAN); // bool(false) Note: The fact that any comparison involving NAN is always … Read more
If you are extending your form from a ModelForm, use the instance keyword argument. Here we pass either an existing instance or a new one, depending on whether we’re editing or adding an existing article. In both cases the author field is set on the instance, so commit=False is not required. Note also that I’m … Read more
Here is a small demo, which shows why this is happenning: In [131]: df = pd.DataFrame(np.random.randint(0,20,(5,2)), columns=list(‘AB’)) In [132]: df Out[132]: A B 0 3 11 1 0 16 2 16 1 3 2 11 4 18 15 In [133]: res = df[‘A’] > 10 In [134]: res Out[134]: 0 False 1 False 2 True … Read more
The comma operator chains multiple expressions together, and the result of the operation is the value of the last operand. The only real use for it is when you need multiple side effects to occur, such as assignment or function calls.