No, there is and has never been an explicit built in option for conversion of Int to Bool, see the language reference for Bool for details. There exists, still, however, an initializer by NSNumber. The difference is that implicit bridging between Swift numeric type and NSNumber has been removed in Swift 3 (which previously allowed … Read more
UPDATE 1: Code that gets me done with 1) (don’t forget tot pass CHOICES to the BooleanField in the model) from main.models import TagCat from django.contrib import admin from django import forms class MyTagCatAdminForm(forms.ModelForm): class Meta: model = TagCat widgets = { ‘by_admin’: forms.RadioSelect } fields=”__all__” # required for Django 3.x class TagCatAdmin(admin.ModelAdmin): form = … Read more
It’s normal behaviour of the language. Quoting the perlsyn manpage: The number 0, the strings ‘0’ and “”, the empty list (), and undef are all false in a boolean context. All other values are true. Negation of a true value by ! or not returns a special false value. When evaluated as a string … Read more
In C#, certainly the bits aren’t packed by default, so multiple bool fields will each take 1 byte. You can use BitVector32, BitArray, or simply bitwise arithmetic to reduce this overhead. As variables I seem to recall they take 4 bytes (essentially handled as int = Int32). For example, the following sets i to 4: … Read more
The other likely size for it is that of int, being the “efficient” integer type for the platform. On architectures where it makes any difference whether the implementation chooses 1 or sizeof(int) there could be a trade-off between size (but if you’re happy to waste 7 bits per bool, why shouldn’t you be happy to … Read more
Apparently .filter() was introduced in ES5. This definitely helped me wrap my mind around what’s going on here. Hope it helps! Essentially, writing: arr.filter(Boolean) is the same as writing: arr.filter( function(x) { return Boolean(x); }); since Boolean() is also a function that returns truthy when true and falsy when false! Example: var a = [1, … Read more
Yes: In C++ (§4.5/4): An rvalue of type bool can be converted to an rvalue of type int, with false becoming zero and true becoming one. In C, when a value is converted to _Bool, it becomes 0 or 1 (§6.3.1.2/1): When any scalar value is converted to _Bool, the result is 0 if the … Read more
Include <stdbool.h> header #include <stdbool.h> int main(void){ bool b = false; } Macros true and false expand to 1 and 0 respectively. Section 7.16 Boolean type and values < stdbool.h > 1 The header <stdbool.h> defines four macros. 2 The macro bool expands to _Bool. 3 The remaining three macros are suitable for use in … Read more
Empty strings are “falsy” (python 2 or python 3 reference), which means they are considered false in a Boolean context, so you can just do this: if not myString: This is the preferred way if you know that your variable is a string. If your variable could also be some other type then you should … Read more