Making readable modifyable code.

[jahboater]

That thing about having to have "return" at the end of a function or not annoys me.

But what about this check at the start:

Code: Select all

if( values == NULL )
   error return .....

1) here there is no meaningful value to put in a "Result" keyword
2) the check has absolutely nothing whatsoever to do with the real purpose of the function - the averaging algorithm.
If I were to write instead:-

Code: Select all

if( values != NULL )
{
   function body
}

Then I have increased the nesting level artificially for the main code - for some logic that is nothing to do with it.
That makes it less readable I think.

The nesting level should reflect the real code logic only.

Yes, yes I know "assert( values != NULL );" would be better, but just to illustrate the point.

[Heater]

PeterO,

Now I'm going to have to write this recursive average example in ALGOL-60

You mean like this:

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# Calculate average value of all elements of a vector using a recursive algorithm #
PROC average recursive = ([] REAL vector) REAL:
BEGIN
    # Get length from upper and lower bounds of vector #
    INT length = UPB vector - LWB vector + 1;

    IF length = 0 THEN
        # Cannot have average of zero length vector #
        0.0
    ELIF length = 1 THEN
        # Base case #
        vector[1]
    ELSE
        # Recurse... #
        ((average recursive(vector[2..]) * (length - 1)) + vector[1]) / length
    FI
END;

BEGIN
    # Test data #
    [] REAL test vector  = (100, 200, 100);

    # The test #
    REAL result = average recursive(test vector);
    print (result)
END

Run like so:

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$ a68g  average.a68g
+1.33333333333333e  +2

Isn't that just beautiful? No messy "length" parameter. No messy and dangerous pointers. Or "return" statement. Or wiggly brackets. Oh and that PROC, "average recursive" is a real thing that can be passed around just like an INT.

Oh my God, I'm back in 1976 !

Sorry that is ALGOL 68. ALGOL 60 was a bit before my time

[jahboater]

Wow impressive - I loved Algol 68 (I used to actually read the revised report!), but I couldn't remember how to program in it now - too long ago.

In C++ perhaps:

average = std::accumulate( x.begin(), x.end(), 0.0 ) / x.size();

works for any arithmetic data type in the array.

[Heater]

Took me a little while to remind myself how to do that. Haven't written an Algol program since about 1981.

Hey, using std:: is cheating. It's not even the recursive algorithm.

[PeterO]

PeterO,

Now I'm going to have to write this recursive average example in ALGOL-60

You mean like this:

No quite, as you noted that's Algol-68.... But not had time to do the Algol-60 version yet....

PeterO

[jahboater]

My first real job was at a university as a systems programmer.
Part of the interview was to write a program, something to do with crystallography in 20 minutes.
I wrote mine in Algol-68, and because of that I was the only one out of 80 applicants to actually complete it.
A number of people chose BASIC and got in an absolutely hopeless mess.

[PeterO]

Here we go...

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RECURSIVE AVERAGE'
BEGIN REAL ARRAY DATA(0:9)'
INTEGER N'
REAL AV'

REAL PROCEDURE AVERAGE (COUNT,VALUES)' 
VALUE COUNT' 
INTEGER COUNT'
REAL ARRAY VALUES'
BEGIN
REAL AV'
    IF COUNT LESSEQ 0 THEN
       AV := 0.0
    ELSE
       AV := (VALUES(COUNT-1)+(COUNT-1)*AVERAGE(COUNT-1,VALUES))/COUNT' 

    AVERAGE := AV'
END'


FOR N := 0 STEP 1 UNTIL 9 DO DATA(N) := N+1'

AV := AVERAGE(10,DATA)'

PRINT ££L?AV=?,SAMELINE,AV'

END'

And the output

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RECURSIVE AVERAGE
FREE STORE= 4630- 6483



AV= 5.5000000


END OF PROGRAM

PeterO

[Heater]

PeterO,

Awesome.

What are you running that on?

[PeterO]

PeterO,
Awesome.
What are you running that on?

Hardware:
Today my emulator for the Elliott 803B.
In the future I'll run it on the real Elliott 803B at TNMOC. (https://www.youtube.com/watch?v=AIxZ1i8pvZI 803 compiling and running a programme).

Sofware: The 803's Algol-60 compiler (A104).

PeterO

[Heater]

Even more awesome.

Can't wait to see it in action.