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Foo is a reference type, where a is initially assigned a reference of a new object, and b is assigned to the same object reference, i.e. bound to the same object as a, therefore, changes through a is also visible to b as well. Afterwards, a is assigned a reference (rebound) to another new object, and now a and b refer to different
So, PHP can have non-consecutively numerically indexed arrays. The keys have to be of integer (floating point numbers are truncated to integer) or string type, while values can be of arbitrary types, including other arrays and objects. The arrays are heterogeneous: a single array can have keys of different types.
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For example, to perform an element by element sum of two arrays, a and b to produce a third c, it is only necessary to write c = a + b In addition to support for vectorized arithmetic and relational operations, these languages also vectorize common mathematical functions such as sine.
Some people (including Guido van Rossum himself) have called this parameter-passing scheme "call by object reference". An object reference means a name, and the passed reference is an "alias", i.e. a copy of the reference to the same object, just as in C/C++. The object's value may be changed in the called function with the "alias", for example:
The object that the variable points to is not influenced by that final variable though. In the above example, the origin's x and y coordinates can be freely modified. To prevent this undesirable situation, a common requirement is that all fields of an immutable object must be final, and that the types of these fields must be immutable themselves.
A reference to a live distributed object is another example: it is a complete specification for how to construct a small software component called a proxy that will subsequently engage in a peer-to-peer interaction, and through which the local machine may gain access to data that is replicated or exists only as a weakly consistent message ...
The assignment statement (=) binds a name as a reference to a separate, dynamically allocated object. Variables may subsequently be rebound at any time to any object. In Python, a variable name is a generic reference holder without a fixed data type; however, it always refers to some object with a type.