Instead of a counting loop, Ruby has the upto method. For example, we could have the following:

1.upto(5) {|x| print x, " "}

This produces the following output:

1 2 3 4 5

Syntax that resembles a for loop in other languages could also be used, as in the following:

for x in 1..5

print x, " "

end

Ruby actually has no for statement—constructs like the above are converted by Ruby into upto method calls.

Now we consider how blocks work. The yield statement is similar to a method call, except that there is no receiver object and the call is a request to execute the block attached to the method call, rather than a call to a method. yield is only called in a method that has been called with a block. If the block has parameters, they are specified in parentheses in the yield statement. The value returned by a block is that of the last expression evaluated in the block. It is this process that is used to implement the built-in iterators, such as times.

8.4 Unconditional Branching

An unconditional branch statement transfers execution control to a specified location in the program. The most heated debate in language design in the late 1960s was over the issue of whether unconditional branching should be part of any high-level language, and if so, whether its use should be restricted. The unconditional branch, or goto, is the most powerful statement for controlling the flow of execution of a program’s statements. However, using the goto carelessly can lead to serious problems. The goto has stunning power and great flexibility (all other control structures can be built with goto and a selector), but it is this power that makes its use dangerous. Without restrictions on use, imposed by either language design or programming standards, goto statements can make programs very difficult to read, and as a result, highly unreliable and costly to maintain.

These problems follow directly from a goto’s capability of forcing any program statement to follow any other in execution sequence, regardless of whether that statement precedes or follows the previously executed statement in textual order. Readability is best when the execution order of statements is