C : is there “lazy evaluation” when using && operator, as in C++?
Yes && is short circuited and you are using it correctly.If next is NULL string compare will never happen.
evaluation
How to evaluate functions in GDB?
The syntax for calling a function in gdb is call pow(3,2) Type help call at the gdb prompt for more information.
Setting extra bits in a bool makes it true and false at the same time
In C++ the bit representation (and even the size) of a bool is implementation defined; generally it’s implemented as a char-sized type taking 1 or 0 as possible values. If you set its value to anything different from the allowed ones (in this specific case by aliasing a bool through a char and modifying its … Read more
Math Expression Evaluation
If you’re “academically interested”, you want to learn about how to write a parser with operator precedence. Simple Top-Down Parsing in Python is a nice article that builds an example parser to do exactly what you want to do: Evaluate mathematical expressions. I can highly recommend having a go at writing your own first parser … Read more
What is the purpose of the unary plus (+) operator in C?
You can use it as a sort of assertion that an expression has arithmetic type: #define CHECK_ARITHMETIC(x) (+(x)) This will generate a compile-time error if x evaluates to (say) a pointer. That is about the only practical use I can think of.
Why does 1+++2 = 3?
Your expression is the same as: 1+(+(+2)) Any numeric expression can be preceded by – to make it negative, or + to do nothing (the option is present for symmetry). With negative signs: 1-(-(2)) = 1-(-2) = 1+2 = 3 and 1-(-(-2)) = 1-(2) = -1 I see you clarified your question to say that … Read more
Using assignment as a condition expression?
C++ — ISO/IEC 14882:2003(E) [5.17/1] There are several assignment operators, all of which group right-to-left. All require a modifiable lvalue as their left operand, and the type of an assignment expression is that of its left operand. The result of the assignment operation is the value stored in the left operand after the assignment has … Read more
SQL UPDATE order of evaluation
MySQL does “left to right” evaluation and does “see” the new values. (Tested on 5.0.45-community-nt-log MySQL Community Edition) Furthermore, from the MySQL manual: “Single-table UPDATE assignments are generally evaluated from left to right. For multiple-table updates, there is no guarantee that assignments are carried out in any particular order.” Now, “generally” is quite vague and … Read more
In Java, what are the boolean “order of operations”?
The Java Tutorials has a list illustrating operator precedence. The equality operators will be evaluated first, then &&, then ||. Parentheses will be evaluated before anything else, so adding them can change the order. This is usually pretty much the same from language to language, but it’s always a good idea to double check. It’s … Read more
Does Python’s `all` function use short circuit evaluation?
Yes, it short-circuits: >>> def test(): … yield True … print(‘one’) … yield False … print(‘two’) … yield True … print(‘three’) … >>> all(test()) one False From the docs: Return True if all elements of the iterable are true (or if the iterable is empty). Equivalent to: def all(iterable): for element in iterable: if not … Read more