This is not possible with a simple DEFAULT value, as the manual clearly states: The value is any variable-free expression (subqueries and cross-references to other columns in the current table are not allowed). You could use a trigger instead: CREATE OR REPLACE FUNCTION trg_foo_b_default() RETURNS trigger LANGUAGE plpgsql AS $func$ BEGIN — For just a … Read more
If a class member is always initialized with the same initial value, then you should make the initializer inline, so as to avoid duplication. If the initial value depends on the constructor, then put it in the constructor initializer list. (And never use assignment in the way you did.) Example: class Foo { bool done … Read more
Why is the default value of the string type null instead of an empty string? Because string is a reference type and the default value for all reference types is null. It’s quite annoying to test all my strings for null before I can safely apply methods like ToUpper(), StartWith() etc… That is consistent with … Read more
You need to use a sentinel to detect that a default value was not set: sentinel = object() def func(someparam, default=sentinel): if default is not sentinel: print(“You passed in something else!”) This works because an instance of object() will always have it’s own memory id and thus is will only return True if the exact … Read more
Python 3: inp = int(input(“Enter the inputs : “) or “42”) Python 2: inp = int(raw_input(“Enter the inputs : “) or “42”) How does it work? If nothing was entered then input/raw_input returns empty string. Empty string in Python is False, bool(“”) -> False. Operator or returns first truthy value, which in this case is … Read more
It is possible to set a function in state using hooks, but because state can be initialized and updated with a function that returns the initial state or the updated state, you need to supply a function that in turn returns the function you want to put in state. const { useState } = React; … Read more
A declared variable can be Zero Initialized, Value Initialized or Default Initialized. In your example: Info *p = new Info(); <——- Value Initialization Info *p = new Info; <——- Default Initialization The C++03 Standard 8.5/5 aptly defines each: To zero-initialize an object of type T means: — if T is a scalar type (3.9), the … Read more
This is covered in detail in a relatively popular SO question, but I’ll try to explain the issue in your particular context. When your declare your function, the default parameters get evaluated at that moment. It does not refresh every time you call the function. The reason why your functions behave differently is because you … Read more
As @Ignacio says, you can’t do this. In your latter example, you might have a situation where None is a valid value for arg2. If this is the case, you can use a sentinel value: sentinel = object() def myfunc(arg1, arg2=sentinel): if arg2 is sentinel: arg2 = arg1 print (arg1, arg2) myfunc(“foo”) # Prints ‘foo … Read more