command "cat": clean and powerful

There are several commands that are very powerful; such as the command "cat".

The word cat comes from the word concatenate; it is commonly used in various languages.  For example, cat in unix connects/links the file content to the monitor. 

 

The cat command can be "infinitely" long; it contains/links a mixture of expressions and statements; the last one is normally an expression, which happens to be the return value.  (sometimes, I wonderwhat  if the right most one is a statement; does it evaluate and return? e.g a=7  does it return a true or false or return a value for the assignment )

Here is an example:

cat(s==0,i==1,while(le(i,N),s==s+p[i],i==i+1), 5*s)

the command line contains two assignments, one loop, one return value.  In plain English, the above line says that we assign 0 to s and 1 to i; then we check whether i is smaller or equal to N or not, if yes, we add up all the p elements, and move up the counter i to the next one; when this thing done, we evaluate the expression 5 multiplied by s and return it if there is a holder for it.

if we write in C++, it may look like this

for (s=0, i=1; i <=N; i++) s+=p[i]; return 5*s;

For a simple loop, one may wonder why bother using cat (my kid used to ask me why write several lines to calculate the sum of 3 numbers, in a similar way); the beauty of using cat is for complicated cases; it is very powerful and it is cleanly structured.  moreover, nesting is permitted.

Imagine the whole thing is named; how more powerful can we get? 

I personally admire the beautiful mind from where these nice things flew out.