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In Haskell, [8] there is no variable assignment; but operations similar to assignment (like assigning to a field of an array or a field of a mutable data structure) usually evaluate to the unit type, which is represented as (). This type has only one possible value, therefore containing no information.
Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
Dynamic environment variables (also named internal variables or system information variables under DOS) are pseudo-environment variables supported by CMD.EXE when command-line extensions are enabled, and they expand to various discrete values whenever queried, that is, their values can change when queried multiple times even within the same ...
Cython also facilitates wrapping independent C or C++ code into python-importable modules. Cython is written in Python and C and works on Windows, macOS, and Linux, producing C source files compatible with CPython 2.6, 2.7, and 3.3 and later versions. The Cython source code that Cython compiles (to C) can use both Python 2 and Python 3 syntax ...
Inline files are referenced as << or <<pathname: the first notation creates a temporary file, the second notation creates (or overwrites) the file with the specified pathname. An inline file is terminated with << on a line by itself, optionally followed by the (case-insensitive) keyword KEEP or NOKEEP to indicate whether the created file should ...
In the initialization part, any variables needed are declared (and usually assigned values). If multiple variables are declared, they should all be the same type. The condition part checks a certain condition and exits the loop if false, even if the loop is never executed. If the condition is true, then the lines of code inside the loop are ...
However, variables declared outside a function have "file scope," meaning they are visible within the file. Variables declared with file scope are visible between their declaration and the end of the compilation unit (.c file) (unless shadowed by a like-named object in a nearer scope, such as a local variable); and they implicitly have external ...
While a variable or function may be declared many times, it is typically defined once (in C++, this is known as the One Definition Rule or ODR). Dynamic languages such as JavaScript or Python generally allow functions to be redefined, that is, re-bound; a function is a variable much like any other, with a name and a value (the definition).