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The types of objects that can be iterated across (my_list in the example) are based on classes that inherit from the library class ITERABLE. The iteration form of the Eiffel loop can also be used as a boolean expression when the keyword loop is replaced by either all (effecting universal quantification) or some (effecting existential ...
Rest parameters are similar to Javascript's arguments object, which is an array-like object that contains all of the parameters (named and unnamed) in the current function call. Unlike arguments, however, rest parameters are true Array objects, so methods such as .slice() and .sort() can be used on them directly.
The reasoning behind this is that if Array is extended via prototype and Object is kept pristine, for and for-in loops will work as expected on associative 'arrays'. This issue has been brought to the fore by the popularity of JavaScript frameworks that make heavy and sometimes indiscriminate use of prototypes to extend JavaScript's inbuilt types.
In addition to support for vectorized arithmetic and relational operations, these languages also vectorize common mathematical functions such as sine. For example, if x is an array, then y = sin (x) will result in an array y whose elements are sine of the corresponding elements of the array x. Vectorized index operations are also supported.
Specifically, the for loop will call a value's into_iter() method, which returns an iterator that in turn yields the elements to the loop. The for loop (or indeed, any method that consumes the iterator), proceeds until the next() method returns a None value (iterations yielding elements return a Some(T) value, where T is the element type).
Several programming languages (e.g., Ada, D, C++11, Smalltalk, PHP, Perl, Object Pascal, Java, C#, MATLAB, Visual Basic, Ruby, Python, JavaScript, Fortran 95 and later) have special constructs which allow implicit looping through all elements of an array, or all members of a set or collection.
In JavaScript, an object is an associative array, augmented with a prototype (see below); each key provides the name for an object property, and there are two syntactical ways to specify such a name: dot notation (obj.x = 10) and bracket notation (obj['x'] = 10). A property may be added, rebound, or deleted at run-time.
This example computes the maximum element of an array. The method's precondition and postcondition are given with the requires and ensures clauses (respectively). Likewise, the loop invariant and loop variant are given through the invariant and decreases clauses (respectively).