Hi,

This should be an easy one but its confusing me unfortunately.

Please can someone tell me what the following constraint is saying?:

1≤N<100

In particular, I don't understand what the 1 <= N means. Does it simply mean N is less than or equal to 1?


Thanks in advance...

N is between 1 and 100 including 1 but not 100. If these are integers you could say that N is between 1 and 99 including both.

Thanks for the reply, Thats kind of what I was thinking, however I am still a little confused when trying to make this syntactically correct in Bash. Given the following:

1T,A,B1000

How would I express this constraint using bash (I want to start from 1)?

it seems I have it all wrong:

for $((1<=T;A;B<=1000; 1++))
do
something
done

or is it:

for ((T >= 1; T<= 1000; A >= 1; A <= 1000; B >=1; B <=1000; 1++ ))
do
something
done



Thanks

So you don't know what 1T,A,B1000 is supposed to mean? Well, where did it come from?

just one additional comment: 1++ is illegal, you need to use a variable not a number as loop index.

1 members found this post helpful.

Sorry guys, looks like the characters I copied did not make it into my post. This is what the constraint was supposed to look like:

1<=T,A,B<=1000

I now understand what this means but do not know how to express this using a bash arithmetic operation. My samples above don't seem to cut it.

So I want to loop through pairs of integers (A and B, separated by a space) T times. Each time adding the two together.

Thanks in advance and apologies for the mistakes above.

forget bash, it requires some actual programming language:

It will be *very* slow though

1 members found this post helpful.

Actually you could do the same in bash:

Even slower of course.

1 members found this post helpful.

Two-and-a-half suggestions:

(1) Use a real programming language. In Unix/Linux you have half-a-dozen (at least) to choose from, and many more are available at no cost. Through the magic of the #!shebang mechanism, any of these can be used to write "a shell command." The Korn shell is the only one which attempted to include a full-featured programming language as its shell-scripting tool.

(2) When you go about writing the thing, don't economize on source-code characters. For example, I think that the example above is unnecessarily terse. There's no advantage whatsoever in creating source code that a human must "puzzle out." There's also no advantage in saving microseconds. Especially in a "real" language, your source code will be efficiently translated into the actual instructions that the computer will execute.

(2-1/2) Liberally include comments in your code. Comments are free. They don't slow-down execution at all, even as they vastly increase readability and understanding.

1 members found this post helpful.

Thanks guys, for the great feedback. I now think I have a grasp (however faint) on setting these up. It is kind of how I thought. i.e. there is no short cut to expressing these constraints correctly.
I have spent a little time trying to learn python (which I guess is a real language), but have since put it on the back burner to try and improve my basic shell scripting..... It may take a while :-P

Cheers! :-)

Could you please post, step by step what you want to happen ? Give an example using small values of A, B, T. I'm sure this can easily be done in awk.