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Python uses the following syntax to express list comprehensions over finite lists: S = [ 2 * x for x in range ( 100 ) if x ** 2 > 3 ] A generator expression may be used in Python versions >= 2.4 which gives lazy evaluation over its input, and can be used with generators to iterate over 'infinite' input such as the count generator function which ...
Infinite loops can be implemented using various control flow constructs. Most commonly, in unstructured programming this is jump back up ( goto ), while in structured programming this is an indefinite loop (while loop) set to never end, either by omitting the condition or explicitly setting it to true, as while (true) ... .
When eager evaluation is desirable (primarily when the sequence is finite, as otherwise evaluation will never terminate), one can either convert to a list, or use a parallel construction that creates a list instead of a generator. For example, in Python a generator g can be evaluated to a list l via l = list(g), while in F# the sequence ...
Python supports conditional execution of code depending on whether a loop was exited early (with a break statement) or not by using an else-clause with the loop. For example, For example, for n in set_of_numbers : if isprime ( n ): print ( "Set contains a prime number" ) break else : print ( "Set did not contain any prime numbers" )
A generator call can then be used in place of a list, or other structure whose elements will be iterated over. Whenever the for loop in the example requires the next item, the generator is called, and yields the next item. Generators don't have to be infinite like the prime-number example above.
Platform-specific JNI mechanisms. These use JNI methods implemented in the OS or C libraries to provide the functionality to the JVM. [citation needed] Thread abstractions. Coroutine libraries which are implemented using threads may be heavyweight, though performance will vary based on the JVM's thread implementation.
Fortran's equivalent of the for loop is the DO loop, using the keyword do instead of for, The syntax of Fortran's DO loop is: DO label counter = first , last , step statements label statement The following two examples behave equivalently to the three argument for-loop in other languages, initializing the counter variable to 1, incrementing by ...
A conditional loop has the potential to become an infinite loop when nothing in the loop's body can affect the outcome of the loop's conditional statement. However, infinite loops can sometimes be used purposely, often with an exit from the loop built into the loop implementation for every computer language , but many share the same basic ...