diamond pattern (BASIC) 1.1
Author: David Payne
Category: Christmas Challenge 2023
System: BBC Micro
Language: BBC BASIC
Len source code: 41 bytes
Len exe file: 41 bytes
Len code only: 41 bytes
Instructions:
Save the VCCC.ssd file on your local PC
From the https://bbc.godbolt.org website
click on Discs
From examples or local
Choose file
select the saved VCCC.ssd file
enter CHAIN"PROGRAM"
Description:
The diamond pattern is 19x19 characters (0 to 18 in the screen coordinates)
the x coordinate is translated into a number from the below table (e.g. x=0 -> 3)
3210123210123210123
the y coordinate is translated into a number from the above table (e.g. y=1 -> 2)
when one of the numbers is 3 and the other one is 0
OR when one of the numbers is 2 and the other one is 1
output an asterisk else output a space
or more simply...
when the 2 numbers add up to 3
output an asterisk else output a space
the one-line program is
1CLS:REPEATVDU32ORABS(POS MOD6-3)+ABS(VPOS MOD6-3)=3ANDPOS<19AND10:UNTILVPOS>18
CLS clears the screen
the REPEAT/UNTIL loop gives us 19 rows
POS and VPOS give the cursor x and y
ABS(POS MOD6-3)+ABS(VPOS MOD6-3)=3
calculates the 2 numbers and checks that their sum is equal to 3
POS<19
gives us 19 columns (it outputs trailing spaces rather than new lines)
the expression
32 OR ABS(POS MOD6-3)+ABS(VPOS MOD6-3)=3 AND POS<19 AND 10 (spaces added for clarity)
gives us 42 (asterisk) or 32 (space)
and we simply output this character to the screen (VDU)
10 days later...
I was messing around with the code and I managed to find an alternative (but shorter) expression for the same pattern:
I replaced:
ABS(POS MOD6-3)+ABS(VPOS MOD6-3)=3
with:
ABS(VPOS^2-POS^2)MOD6=3 (^ = raise to the power of)
The program runs slower, but more importantly, it is 7 bytes shorter
The program is now:
1CLS:REPEATVDU32ORABS(VPOS^2-POS^2)MOD6=3ANDPOS<19AND10:UNTILVPOS>18
Comments:
Thanks to Logiker for organising another fun contest and a Happy Christmas to all contestants
1CLS:REPEATVDU32ORABS(VPOS^2-POS^2)MOD6=3ANDPOS<19AND10:UNTILVPOS>18