10 PRINT big maze in Color BASIC – part 1

See also: part 1, part 2, part 3 and part 4.

Awhile back, I discussed the famous Commodore 10 PRINT one-line program, inspired by a YouTube video from 8-Bit Show and Tell.

Commodore PET running the 10 PRINT program.

Although most computers could do the same program in BASIC, unless your system had those wonderful diagonal graphics characters, the result could be a bit lacking.

Scrolling maze… Sorta.

On the CoCo, using the 2×2 block graphics characters was not an improvement, either.

But perhaps if you used a 4×4 block it might look more like a maze. This allows 16 maze characters across by 8 down (versus a Commodore VIC-20 with 22×23).

4×4 Maze

Well, it works, but takes up much more than one line. How small can you make it? Here is my version:

0 ' BIGMAZE.BAS
10 C=2
20 B$=CHR$(128)
30 L$=CHR$(128+16*C+9)
40 R$=CHR$(128+16*C+6)
50 M$(0,0)=B$+R$:M$(0,1)=R$+B$
60 M$(1,0)=L$+B$:M$(1,1)=B$+L$
70 P=512-32*2
80 M=RND(2)-1
90 PRINT@P,M$(M,0);:PRINT@P+32,M$(M,1);
100 P=P+2:IF P>479 THEN PRINT:GOTO 70
110 GOTO 80

Make it smaller. Make it faster. Share your work. And someone tell Jim Gerrie since he probably has already done this…

Until next time…

Odd or Even in Color BASIC?

In my 3X+1 post, I needed to check if a value was odd or even. I did so by using “AND 1” which would test the least significant bit. This works, and is fast, but is limited to values 32767 or lower (15 bits).

Comments from William Astle, RogelioP and John offered corrections and updates to my code. I decided to benchmark a few different methods for detecting if a value was odd or even, and here is what I came up with.

0 REM 3x+1 Benchmarking

5 'GOTO 300

100 ' 0-32767 ONLY
110 TIMER=0
120 FOR A=1 TO 1000
130 IF X AND 1 THEN REM
140 NEXT:PRINT TIMER

200 ' ALL RANGES?
210 TIMER=0
220 FOR A=1 TO 1000
230 IF INT(X/2)=X/2 THEN REM
240 NEXT:PRINT TIMER

300 ' ROGELIO P
310 TIMER=0
320 FOR A=1 TO 1000
330 IF INT(X/2)*2=X THEN REM
340 NEXT:PRINT TIMER

400 ' WILLIAM ASTLE
405 T=0:H=0.5
410 TIMER=0
420 FOR A=1 TO 1000
430 T=X*H:IF T=INT(T) THEN REM
440 NEXT:PRINT TIMER

500 ' DIVIDE TEST
505 T=0:H=2
510 TIMER=0
520 FOR A=1 TO 1000
530 T=X/H:IF T=INT(T) THEN REM
540 NEXT:PRINT TIMER

When I run this program in Xroar on my Raspberry Pi 400, I get:

313
508
506
485
485

As expected, AND is the fastest, so use this if you know your values will be 32767 or lower.

Using INT(X/2)=X/2 was a fraction slower as INT(X/2)*2=X, which I guess makes sense since both do an INT and two math functions.

William’s suggestion of multiplying by .5 instead of dividing by two rang a bell. I believe he (or someone) pointed this out to me a few years ago when I was doing similar benchmarks. A big speed up comes just from putting the value in a variable, but I was surprised to see that dividing by a variable of 2 was the same speed as multiplying by a variable of .5.

What ideas do you have? Anything with math (“/2”) can be sped up by using a variable (“/H”), so there are some improvements just from that. Using HEX values (“&H2”) instead of decimal is also faster, as is removing extra spaces.

But are there better approaches we can use?

Thoughts appreciated.

3X+1 in C#

For my day job, I do embedded C programming for PIC24 compilers and some Windows C programming in something called LabWindows. Lately, I’ve been touching some C# stuff, so I decided to revisit last night’s 3X+1 program by converting it to C#.

You can compile and run it online here: https://www.onlinegdb.com/online_csharp_compiler

// 3X+1

using System;
					
public class Program
{
	public static void Main()
	{
		while (true)
		{
			Int32 x = 0;

			Console.WriteLine();
			Console.Write("STARTING NUMBER? ");
			x = Int32.Parse(Console.ReadLine());
			
			while (true)
			{
				Console.Write(x);
				Console.Write(" ");
				
				if (x == 1) break;
				
				if ((x & 1) == 1) // Odd
				{
					x = x * 3 + 1;
				}
				else // Even
				{
					x = x / 2;
				}
			}
		}
	}
}

3X+1 and Color BASIC

For the past three weeks, I have found myself out-of-town for work. This week, I decided to bring my Raspberry Pi 400 along so I could play with it in the hotel room.

Raspberry Pi 400

I soon found myself toying around with the XRoar CoCo emulator, and I knew just what I wanted to program…

Last night, YouTube showed me a video about “the most dangerous problem in mathematics.”

The idea is you start with a number. If it is odd, you multiply it by 3 and add 1. If it is even, you divide it by 2. Repeat until you get to the pattern 4, 2, 1, 4, 2, 1, 4, 2, 1.

Math says that, so far, every number ends up at that pattern. No one has figured out a formula that leads to any number that does not end at 4, 2, 1.

With that in mind, I thought it would be fun to write the 3X+1 problem in CoCo Color BASIC. It looks like this:

0 REM 3X+1
10 PRINT:INPUT "STARTING NUMBER";X
20 PRINT X;
30 IF X=1 THEN 10
40 IF X AND 1 THEN X=X*3+1:GOTO 20
50 X=X/2:GOTO 20 

I tried to avoid using any Extended Color BASIC features such as HEX numbers (&H1) to speed things up. I even skipped ELSE so it could run on a VIC-20 or other system without that command.

I use “X AND 1” to test for a number being odd. Any odd number has the first bit set. 1 (00000001) does, 2 does not (00000010), 3 does (00000011), and so on.

It does have one flaw… if any number is greater than 32767, it will crash with a ?FC ERROR. Apparently Color BASIC’s AND cannot handle any value greater than 7 bits (01111111 = 32767).

Do you know of a different way to test for even or odd values? I can think of two, one of which would be terribly inefficient and the other not as inefficient but much worse than using AND.

Give it a shot and see if you can find the largest sequence of numbers a CoCo can calculatae.

Or better yet, find a better way to do this in Color BASIC.

Enjoy!

Arduino Serial output C macros

Here is a quickie.

In Arduino, instead of being able to use things like printf() and puchar(), console output is done by using the Serial library routines. It provides functions such as:

Serial.print();
Serial.println();
Serial.write();

These do not handle any character formatting like printf() does, but they can print strings, characters or numeric values in different formats. Where you might do something like:

int answer = 42;
printf("The answer is %d\r\n", answer);

…the Arduino version would need to be:

int answer = 42;
Serial.print("This answer is ");
Serial.print(answer);
Serial.println();

To handle printf-style formatting, you can us sprintf() to write the formatted string to a buffer, then use Serial.print() to output that. I found this blog post describing it.

I recently began porting my Arduino Telnet routine over to standard C to use on some PIC24 hardware I have at work. I decided I should revisit my Telnet code and try to make it portable, so the code could be built for Arduino or standard C. This would mean abstracting all console output, since printf() is not used on the Arduino.

I quickly came up with these Arduino-named macros I could use on C:

#include <stdio.h>
#include <stdlib.h>

#define SERIAL_PRINT(s)     printf(s)
#define SERIAL_PRINTLN(s)   printf(s"\r\n")
#define SERIAL_WRITE(c)     putchar(c)

int main()
{
    SERIAL_PRINT("1. This is a line");
    SERIAL_PRINTLN();
    SERIAL_PRINTLN();

    SERIAL_PRINTLN("2. This is a second line.");

    SERIAL_PRINT("3. This is a character:");
    SERIAL_WRITE('x');
    SERIAL_PRINTLN();

    SERIAL_PRINTLN("done.");

    return EXIT_SUCCESS;
}

Ignoring the Serial.begin() setup code that Arduino requires, this would let me replace console output in the program with these macros. For C, it would use the macros as defined above. For Arduino, it would be something like…

#define SERIAL_PRINT(s)     Serial.print(s)
#define SERIAL_PRINTLN(s)   Serial.println(s)
#define SERIAL_WRITE(c)     Serial.write(c)

By using output macros like that, my code would still look familiar to Arduino folks, but build on a standard C environment (for the most part).

This isn’t the most efficient way to do it, since Arduino code like this…

  Serial.print("[");
  Serial.print(val);
  Serial.println("]");

…would be one printf() in C:

printf ("[%d]\n", val);

But, if I wanted to keep code portable, C can certainly do three separate printf()s to do the same output as Arduino, so we code for the lowest level output.

One thing I don’t do, yet, is handle porting things like:

Serial.print(val, HEX);

On Arduino, that outputs the val variable in HEX. I’m not quite sure how I’d make a portable macro for that, unless I did something like:

#define SERIAL_PRINT_HEX(v) Serial.print(v, HEX)

#define SERIAL_PRINT_HEX(v) printf("%x, v)

That would let me do:

SERIAL_PRINT("[");
SERIAL_PRINT_HEX(val);
SERIAL_PRINTLN("]");

I expect to add more macros as-needed when I port code over. This may be less efficient, but it’s easier to make Arduino-style console output code work on C than the other way around.

Cheers…

C: (too) many happy returns…

Here’s another quick C thing…

One of the jobs I had used a pretty complete coding style guide for C. One of the things they insisted on was only one “return” in any function that returns values. For example:

int function(int x)
{
   if SOMETHING
   {
      return 100;
   }
   else SOMETHING ELSE
   {
      return 200;
   }
   else
   {
      return 0;
   }
}

The above function returns values 100, 200 or 0 based on the input (1, 2 or anything else). It has three different places where a value is returned. This saves code, compared to doing it like this:

int function(int x)
{
   int value;

   if SOMETHING
   {
      value = 100;
   }
   else if SOMETHING ELSE
   {
      value = 200;
   }
   else
   {
      value = 0;
   }

   return value;
}

Above, you see we use a variable, and then have three places where it could be set, and then we return that value in one spot at the end of the function. This probably generates larger code and would take longer to run than the top example.

But if you can afford those extra bytes and clock cycles, it is a much better way to do this — at least form a maintenance and debugging standpoint.

I have accepted this, but only today did I run in to a situation where this approach would have saved me some time and frustration. In my case, I was encounter a compiler warning about a function not returning a value where it was defined to return a value. I looked and confirmed the function was indeed returning a value. What was going on?

The problem was that it used multiple returns, and did something like this:

int function(int x)
{
   int value;

   if (!ValueIsValid(x)) return;

   if SOMETHING
   {
      value = 100;
   }
   else if >OMETHING ELSE
   {
      value = 200;
   }
   else
   {
      value = 0;
   }

   return value;
}

Somewhere in the program was a check that just did a “return” and the compiler was seeing that, but my eyes were looking at the lower portion of the program where a value was clearly being returned.

I am guessing the function originally did not return a value, and when a return value was added later, that initial “return;” was not corrected, leaving a compiler warning. This warning may have been in the code for a long time and was simply left alone because someone couldn’t figure it out (my situation) or wasn’t concerned about compiler warnings.

Today, the warning bugged me enough that I did a deep dive through the function, line-by-line, trying to figure out what was going on. And I found it. A simple correction could have been this:

int function(int x)
{
   int value;

   if (!ValueIsValid(x)) return 0; // FIXED: Add missing return value.

   if SOMETHING
   {
      value = 100;
   }
   else if SOMETHING ELSE
   {
      value = 200;
   }
   else
   {
      value = 0;
   }

   return value;
}

That resolved the compiler warning, but still left two spots where a value was returned, so I ended up doing something like this:

int function(int x)
{
   int value;

   if (ValueIsValid(x) == true) // do this if valid
   {
      if SOMETHING
      {
         value = 100;
      }
      else SOMETHING ELSE
      {
         value = 200;
      }
      else
      {
         value = 0;
      }
   }
   else // Not valid
   {
      value = 0;
   }

   return value;
}

Now there is only one place the function returns, and it only processeses things if the initial value appears valid.

I will sleep better at night.

I sleep on a soap box.

GEEKPI’s Getting Started with MicroPython on Raspberry Pi Pico kit

It seems only yesterday I first mentioned the new Raspberry Pi Pico. At this time of its introduction, I wondered two things:

  1. Why did they use the “Raspberry Pi” name for a new piece of hardware that does not run Linux. It was closer to an Arduino than a Pi. I expect this naming will cause confusion, since folks have had years learning what a “Pi” can do (video, audio, keyboard, mouse, etc.) and the Pico does none of that.
  2. Why did they bother with a $4 Pico, if a PiZero can be had for only $1 more.

#2 is answered with “because folks like me dislike the slowness of booting a full OS and all the hassles of dealing with Linux for an embedded project.” However, I already use Arduinos for that purpose. The Pico just seemed more like the larger Arduino models.

Side Note: To me, and many others, “Arduino” will always mean “Arduino Uno“, the tiny and cheap Arduino with 4K of RAM. Because it was the version that started things up, the name Arduino is mostly associated with these smaller limited models. But, Arduino even makes more powerful versions that can run Linux.

#1 I think is “just because it will cause confusion.” I think the same thing about the “new” Atari VCS. (If you didn’t know, there is a new Atari out — and it is called the same thing the original Atari VCS was called back in 1977. No confusion there. ;-)

But I digress…

I recently received a $45 GEEKPI BASIC Pico kit to review. You can find it on Amazon (see that link).

Reading through the specs of this $4 circuit board, I find it is pretty impressive. Speeds up to 133MHz, 264K of RAM, and 2MB of Flash storage. It has enough power, memory and storage to run things like Python, which a 4K Arduino just cannot do.

The included manual had me download a Python IDE, then plug up and connect to the Pico with a USB cable. I could then type and run my first “Hello World” program in Python. You can even copy the “main.py” python script to the Pico so it will power up and run on it’s own. (A few other steps were needed to install MicroPython on the Pico, but they were easy and only took a few minutes.)

Impressive.

The initial downside is that the Pico does not come with the header pins soldered on. I had to turn to a coworker to do this for me so I could plug it into the breadboard and hook up some wires for a blinking LED example.

I expect at some point (if not already) you will be able to buy a model with those pins already soldered on, much like you can do with a Pi Zero.

I do not know when I’ll have time to fully explore the “power of the Pico,” but it looks like it will be a fun time. It appears to be quite capable with I/O and protocols (SPI, I2C, UARTs, etc.).

More to come…

char versus C versus C#

Updates:

  • 2020-07-16 – Added a few additional notes.

I am mostly a simple C programmer, but I do touch a bit of C# at my day job.

If you don’t think about what is going on behind the scenes, languages like Java and C# are quite fun to work with. For instance, if I was pulling bytes out of a buffer in C, I’d have to write all the code manually. For example:

Buffer: [ A | B | C | D | D | E | E | E | E ]

Let’s say I wanted to pull three one-byte values out of the buffer (A, B and C), followed by a two-byte value (DD), and a four byte value (EEEE). There are many ways to do this, but one lazy way (which breaks if the data is written on a system with different endianness to how data is stored) might be:

#include <stdint.h>

uint8_t a, b, c;
uint16_t d;
uint32_t e;

a = Buffer[0];
b = Buffer[1];
c = Buffer[2];
memcpy (&d, &Buffer[3], 2);
memcpy (&e, &Buffer[5], 4);

There is much to critique about this example, but this post is not about being “safe” or “portable.” It is just an example.

In C#, I assume there are many ways to achieve this, but the one I was exposed to used a BitConverter class that can pull bytes from a buffer (array of bytes) and load them in to a variable. I think it would look something like this:

UInt8 a, b, c;
UInt16 d;
UInt32 e;

a = Buffer[0];
b = Buffer[1];
c = Buffer[2];
d = BitConverter.ToInt16(Buffer, 3);
e = BitConverter.ToInt32(Buffer, 5);

…or something like that. I found this code in something new I am working on. It makes sense, but I wondered why some bytes were being copied directly (a, b and c) and others went through BitConverter. Does BitConverter not have a byte copy?

I checked the BitConverter page and saw there was no ToUInt8 method, but there was a ToChar method. In C, “char” is signed, representing -127 to 128. If we wanted a byte, we’d really want an “unsigned char” (0-255), and I did not see a ToUChar method. Was that why the author did not use it?

Here’s where I learned something new…

The description of ToChar says it “Returns a Unicode character converted from two bytes“.

Two bytes? Unicode can represent more characters than normal 8-bit ASCII, so it looks like a C# char is not the same as a C char. Indeed, checking the Char page confirms it is a 16-bit value.

I’m glad I read the fine manual before trying to “fix” this code like this:

Char a, b, c;
UInt16 d;
UInt32 e;

// The ToChar will not work as intended!
a = BitConverter.ToChar(Buffer, 0); //Buffer[0];
b = BitConverter.ToChar(Buffer, 1); //Buffer[1];
c = BitConverter.ToChar(Buffer, 2); //Buffer[2];
d = BitConverter.ToInt16(Buffer, 3);
e = BitConverter.ToInt32(Buffer, 5);

For a C programmer experimenting in C# code, that might look fine, but had I just tried it without reading the manual first, I’d have been puzzled why it was not copying the values I expected from the buffer.

Making assumptions about languages, even simple things like a data type “char”, can cause problems.

Thank you, manual.

Researching 8-bit floating point.

Recently, I ran in to a situation where a floating point value (represent current) was being converted to a byte value before being sent off in a status message. Thus, any calculations on the other side were being done with whole values (1, 2, 42, etc.). I was asked if the precision could be increased (adding a decimal place) and realized “you can’t get there from here.”

This made me wonder how much could be done with an 8-bit floating point representation. A quick web search led me to this article:

http://www.toves.org/books/float/

I also found a few others discussion other methods of representing a floating point value with only 8-bits.

Now I kinda want to code up such a routine in C and do some tests to see if it would be better than our round-to-whole-number approach.

Has anyone reading this already done this? I think it would be a fun way to learn more about how floating point representation (sign, mantissa, exponent) works.

But it doesn’t seem very useful.