<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><blockquote type="cite"><blockquote type="cite"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">What is the reason for not offering a looping construct in racket? For</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">example, something like:</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">(loop (i 1 10) (print i))</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Just for the masses, it seems simpler to use.</div></blockquote></blockquote><br>Simpler than what?  For what application?</div><div><br></div><div>The classic C/C++/Java "for" loop was designed for, and is almost always used for, integer counters stepping through an array.  In most of these applications, what you really want to do is "do something to each element of this array," or perhaps "do something to each element of this array until you find one that meets this criterion."</div><div><br></div><div>One of my general principles of programming is "try to avoid introducing concepts in the solution that weren't part of the problem."  In both of the above cases, the problem statement doesn't say anything about integer counters, indices, or mutation, so one should be able to solve the problem without those things.</div><div><br></div><div>In a low-level language like C or Pascal, one can't hide the fact that arrays are indexed with integers, and the way to do something with various different integers is a for-loop.  C++ starts to address the problem with "iterators", which still act like mutable counters and are still used in classic "for" loops, but at least they hide the array indexing.  Java does the same thing with "Iterable" and goes a step farther with "foreach" loops, which partially hide the mutation as well... but anyone who's ever tried defining a class that implements Iterable found that it still has to use mutation internally.  Scheme/Racket's list and sequence operations -- "map", "filter", "foldr", "for", "in-range", "in-naturals", "in-string", "stop-before", etc. -- are yet another step in the direction of eliminating concepts from the solution that weren't in the problem.</div><div><br></div><div>In other words, what's "simpler" is to use a construct that says what you mean.  If you want to print the integers 1 through 10 in increasing order (actually a fairly artificial problem whose main purpose is to test integer-counting for-loop constructs), use "for" and "in-range".  If you want to do something to each element of a list and get a list of the results, use "map".  If you want to extract the elements of a list that meet a particular criterion, use "filter".  If you want to count the elements of a list that meet a particular criterion, use "count-if".  And in the unlikely event that what you want to do doesn't match any of the defined constructs, Scheme/Racket allows you to write your own control constructs (indeed, I have assigned my CS0 students to write their own versions of "map", "filter", and "count-if").</div><div><br></div><div> <div style="font-size: 12px; ">Stephen Bloch</div><div style="font-size: 12px; "><a href="mailto:sbloch@adelphi.edu">sbloch@adelphi.edu</a></div></div></body></html>