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How to write a program to output multiple results
10-25-2020, 03:52 AM
Post: #1
How to write a program to output multiple results
As we all know, when you write a program, you can use the return statement to return the result you want.But is there a way to return multiple results to a CAS or HOME interface (not a terminal)?For example, I write an output program that contains a return instruction that can be called to return a result.But when I write another program that puts an output program in a for loop, it still has only one result on the CAS or HOME interface. Why is that?Theoretically, I've called the output program multiple times, and it should produce multiple results.
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10-25-2020, 06:47 PM
Post: #2
RE: How to write a program to output multiple results
The approach of the Prime built in functions is to return a list. See EIGENVV for example.

RETURN {val1, val2, val3}

You can also dynamically build the list with an arbitrary number of values with the CONCAT function.

Thibault - not collector but in love with the few HP models I own - Also musician : http://walruspark.co
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10-26-2020, 03:35 AM
Post: #3
RE: How to write a program to output multiple results
(10-25-2020 06:47 PM)pinkman Wrote:  The approach of the Prime built in functions is to return a list. See EIGENVV for example.

RETURN {val1, val2, val3}

You can also dynamically build the list with an arbitrary number of values with the CONCAT function.

Thank you for your guidance. I will learn this skill
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10-26-2020, 10:27 AM (This post was last modified: 10-26-2020 10:55 AM by pinkman.)
Post: #4
RE: How to write a program to output multiple results
Here is a small example. FIBO calculates the Fibonacci values between two numbers and returns the values as a list.

Usage example: FIBO(50, 250)
Returns: {55,89,144,233}

Code:

EXPORT FIBO(fstart, fend)
BEGIN
 LOCAL a := 1, b := 1, c := 1, ret := {};
 IF fend >= fstart AND fend >= 0 THEN
  WHILE c <= IP(fend) DO
   IF c >= fstart THEN
    ret := CONCAT(ret, c);
   END;
   c := a + b;
   a := b;
   b := c; 
  END; 
 END;
 RETURN ret; 
END;

Thibault - not collector but in love with the few HP models I own - Also musician : http://walruspark.co
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10-26-2020, 11:32 AM
Post: #5
RE: How to write a program to output multiple results
(10-26-2020 10:27 AM)pinkman Wrote:  Here is a small example. FIBO calculates the Fibonacci values between two numbers and returns the values as a list.

Usage example: FIBO(50, 250)
Returns: {55,89,144,233}

Code:

EXPORT FIBO(fstart, fend)
BEGIN
 LOCAL a := 1, b := 1, c := 1, ret := {};
 IF fend >= fstart AND fend >= 0 THEN
  WHILE c <= IP(fend) DO
   IF c >= fstart THEN
    ret := CONCAT(ret, c);
   END;
   c := a + b;
   a := b;
   b := c; 
  END; 
 END;
 RETURN ret; 
END;

I recreated the FIBO program on my Prime, and now I've learned to return multiple values, thank you very much!
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10-26-2020, 12:49 PM
Post: #6
RE: How to write a program to output multiple results
(10-26-2020 10:27 AM)pinkman Wrote:  ret := CONCAT(ret, c);

CONCAT builds a new list, combining ret and c, using time of O(len(ret) + len(c))
We might speed it up by building nest-list, then flatten it.

ret := {{}}; // list of list
...
ret[0] := {ret[0], c}; // inplace update, not building long list (assumed 0-based indexing)
...
return flatten(ret);

Example:
XCas> lst := [[]]
XCas> lst[0] := [lst[0], [1,2,3]]
XCas> lst[0] := [lst[0], [4,5,6]]
XCas> flatten(lst)

[1,2,3,4,5,6]
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10-26-2020, 01:23 PM
Post: #7
RE: How to write a program to output multiple results
Yes good approach, but there is no flatten function on the Prime.
I also wanted to avoid using CAS functions in a Home HPPL program, because of the isolation of both environments.

Thibault - not collector but in love with the few HP models I own - Also musician : http://walruspark.co
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10-26-2020, 02:51 PM
Post: #8
RE: How to write a program to output multiple results
There is not a flatten built-in, but you will find a couple of LIST FLATTEN functions here:
https://www.hpmuseum.org/forum/thread-9411.html

Stephen Lewkowicz (G1CMZ)
ANDROID HP Prime App broken offline on some mobiles
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10-26-2020, 06:54 PM
Post: #9
RE: How to write a program to output multiple results
(10-26-2020 01:23 PM)pinkman Wrote:  Yes good approach, but there is no flatten function on the Prime.
We should request it ! Big Grin

I was looking at XCas source misc.cc, I discovered there is an undocumented flatten1

XCas> flatten1([1,2,3,[4,[5]]])       → [1,2,3,4,[5]]

The code also explained why flatten is so fast.
It only scan the list 1 time, adding 1 element at a time, with time complexity of O(n)

We could emulate the functionality of flatten, but time complexity is O(n^2)
Here is a simple implementation. (note that concat is needed, which kills performance.)
Code:
flat(lst) := {
  local h := head(lst);
  return (h == lst) ? h : concat(flat(h), flat(tail(lst)));
}
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10-27-2020, 04:55 AM
Post: #10
RE: How to write a program to output multiple results
(10-26-2020 06:54 PM)Albert Chan Wrote:  
(10-26-2020 01:23 PM)pinkman Wrote:  Yes good approach, but there is no flatten function on the Prime.
We should request it ! Big Grin

I was looking at XCas source misc.cc, I discovered there is an undocumented flatten1

XCas> flatten1([1,2,3,[4,[5]]])       → [1,2,3,4,[5]]

The code also explained why flatten is so fast.
It only scan the list 1 time, adding 1 element at a time, with time complexity of O(n)

We could emulate the functionality of flatten, but time complexity is O(n^2)
Here is a simple implementation. (note that concat is needed, which kills performance.)
Code:
flat(lst) := {
  local h := head(lst);
  return (h == lst) ? h : concat(flat(h), flat(tail(lst)));
}

The discussion is a little difficult for me to understand, so I will continue my study
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