How to swap text based on patterns at once with sed?
Maybe something like this: Replace ~ with a character that you know won’t be in the string.
syntax
What does the “Just” syntax mean in Haskell?
It’s actually just a normal data constructor that happens to be defined in the Prelude, which is the standard library that is imported automatically into every module. What Maybe is, Structurally The definition looks something like this: That declaration defines a type, Maybe a, which is parameterized by a type variable a, which just means that you can … Read more
Prolog “or” operator, query
you can ‘invoke’ alternative bindings on Y this way: Note the parenthesis are required to keep the correct execution control flow. The ;/2 it’s the general or operator. For your restricted use you could as well choice the more idiomatic that on backtracking binds Y to each member of the list. edit I understood with … Read more
Meaning of *& and **& in C++
That is taking the parameter by reference. So in the first case you are taking a pointer parameter by reference so whatever modification you do to the value of the pointer is reflected outside the function. Second is the simlilar to first one with the only difference being that it is a double pointer. See … Read more
PHP syntax question: What does the question mark and colon mean? [duplicate]
This is the PHP ternary operator (also known as a conditional operator) – if first operand evaluates true, evaluate as second operand, else evaluate as third operand. Think of it as an “if” statement you can use in expressions. Can be very useful in making concise assignments that depend on some condition, e.g. There’s also … Read more
bash: syntax error near unexpected token `(‘ – Python
Are you typing this at the unix command prompt? You should be doing this inside the python environment, ie. type python at the prompt and work from there. Also, no ; needed at the end of the line in Python
What are those pipe symbols for in Ruby?
They are the variables yielded to the block. Which outputs “5”. A more arcane example: The output is “9”.
Why virtual & static keywords aren’t allowed outside class declaration?
The modifiers must be on the function declarations, otherwise it would be impossible to call the functions given just the declarations. Since they must be on the declarations, it would be redundant to put them on the definitions as well. There’s no particularly good reason to disallow them (as long as they match the declaration), … Read more
Why am I getting an ‘Else without previous if’ error within a for loop?
else doesn’ take any condition, but you’ve written this: which doesn’t do what you intend it to do. You want to do thos: Notice the difference. Also, there can be at most one else block, associated with an if block Or a chain of if, else-if, else-if blocks. That is, you can write this: Or, … Read more
How to get rows and columns count of a 2D array in Java?
Well you probably want array_name.length for getting the count of the rows and array_name[0].length for the columns. That is, if you defined your array like so: