Basic Mel Script Help!

[cabritozavala]

I'm taking a basic MEL scripting class and we were assigned the following problem:

Use rand(0,1) to generate an array of 100 random floating numbers (between 0 and 1).
Then find the maximum values of the array and print out the maximum value AND its
index in the array.

I haven't been able to solve the problem, I know I'm supposed to use the "for" loop but I just haven't been able to start.
Any help would be appreciated.

Thanks

[daniel-faust]

Read what the mel section in the documentation has to say about the for keyword, because letting others solve your problems is the wrong way to learn mel.

Anyway, basically you need to split your problem into smaller parts:

1) how do I use the rand function
2) what is an array
3) how do I create an array
4) how do I insert elements into an array
5) how do I read elements in an array
6) how do I determine the size of an array
7) how do I use the for keyword
8) what is the ideal variable type to be used as a counter
9) how do I increment the value of the counter
10) how do I store the maximum value
11) how do I compare values
12) how do I print the value contained in a variable

[cabritozavala]

I didn't want it to be solved for me, just wanted a push in the right direction.

[gmask]

the typical "for" loop looks like this and you will use this for alot of things in MEL

for example

for($n in ls -sl){

print($n+"\n");
}

this will print out on individual lines each item you have selected

you would probably use the for loop to scan the array for maximum values

to explain the example above further..

ls -sl produces and array and is shorthand for the following

$list = ls -sl;
for($n in $list){

print($n+"\n");

}

whereas $n is just a variable that is assigned what the first item in the list is.

But in order for you to build the array you will probably need a while loop.. something like the following

while($x <=99){
print($x+"\n");
$x++;
}

this will count up to a hundred and print out the value of $x.

$x++ increments the value of $x by one and is equivalent to $x=$x+1.

Inside such a loop you would have your rand statement and increment the index value of your array I'll let you figure that part out.

[daniel-faust]

QUOTE(cabritozava @ 08/15/07, 10:54 PM) [snapback]271637[/snapback]
I didn't want it to be solved for me, just wanted a push in the right direction.

Ok, maybe I sounded rude, I apologize for that.

It was just a bit surprising to read the post which actually seemed to imply that you did not even bother to take a look at the documentation. It covers arrays, flow control, and almost everything you need to know. In addition to the example scripts in the documentation, every documented command contains an example of how to use it.

So I'm just wondering what you have been taught during that first class.

[gmask]

it'll take more than reading about a for loop to perform this task.. now that I think about it you could probably do it without a for loop .. you could creat the array and determine what the highest value is within the while loop.

[joojaa]

Well theres really no difference between a for and while loop in capabilities.

Just for loops are assumed to iterate trough all its members and while is not to be assumed to do so. (thisway you can read programs easier without missing exits)

[ewerybody]

btw: cabritozavala? please give your threads useful names in the future. There are so many threads called help somehow. No one who is searching stuff will have any clue whats in here.

[gmask]

QUOTE(Joojaa @ 08/16/07, 04:15 AM) [snapback]271676[/snapback]
Well theres really no difference between a for and while loop in capabilities.

apples and oranges are both fruits but if I order a screwdriver I'll need an orange

[daniel-faust]

QUOTE
apples and oranges are both fruits but if I order a screwdriver I'll need an orange

I don't get it. There's nothing a for loop can't do what a while loop can do. I'm not talking about the for-in loop since that one's just a handy little gift to the developer anyway.

[gmask]

well there must be some reason why we have a for and a while loop but I don't feel like arguing over the syntactical and semantical differences

[daniel-faust]

Yuck! I completely agree

[ewerybody]

istn't it that way:

for - if you know how much loops you need
while - if you don't know yet how long the loop will go

I mean.. maybe you can have a for loop act the same way if you set the condition that way you'd do in a while-loop. But I always handled it that ^ way. I heard there are languages where you don't even need something else than for-loops (comprehensible to me)

[gmask]

Part of it for me is which one of these loops will allow me to type the least number of characters.. I could for example perform this entire excercise without even using a loop but that would just be plain silly.

[ewerybody]

you could do a loop that creates the code for each line!
That'd be more performant at runtime as well

[joojaa]

Yes but as ai said theres no difference for the computer you can do exactly the same things with both.

its rather just a reading aid! if you see while you know it can terminate halfway, if you see for you assume it runs trough. It does not have to but its a computing convention to help you read other peoples code. As a matter of fact you only ever need one loop type.

But it makes reading and writing of code easier.

fo having a code

CODE
for(yadayada){
  yadayada
  if condition
     break;
}

is considered bad form because you used a for loop wich is assumed to be the iteration set (dont confuse code reader on purpose, your just digging yourself a grave) whereas

CODE
while(something){
  yadayada
  if condition
    something=False;    
}

and
CODE
do{
  yadayada
  if condition
    something=False;    
} while(something)

are expressibly assumed to decide termination for themselves like is:

CODE
while(true){
  yadayada
  if condition
    break;    
}

no other difference, they are just reading aids. Its a way for people to be able to more effectively read your code, no biggie in scripting but can be in a big coding effort.

Dont abuse it. While it does not affect the running of your code it helps you maintain it. you dont need many kinds of loops 1 is enough. But its usefull.

[gmask]

The funny part is that the point of this excercise is to learn about arrays.

here's how not to do it

$junk=<>

lol

[joojaa]

QUOTE(gmask @ 08/17/07, 06:16 PM) [snapback]271789[/snapback]
The funny part is that the point of this excercise is to learn about arrays.

yes tough in practice arrays are almost married to looping in coding terms