rule110.spar

// Triangle side length (stored at mem[9900] thru mem[9908])
//          |
//          V
mem 9900 +  300  storeq

// Initialize column pattern
// The column pattern is simply a condition for each
//   column that is being drawn, in the form of a bit.
// It is updated throughout runtime, causing the fancy drawing
//   you see in the output to appear.
// Example pattern: 11000010
// Example output:  **    * 

// Build initial table
//   Store a `1` at the first byte of memory
mem 1                    + 1 storeb
//   Store a `1` at (amount of columns - 1) in memory
mem mem 9900 + loadq 1 - + 1 storeb

// Construct end of string in memory
mem mem 9900 + loadq + 10000 +     10 storeb // newline
mem mem 9900 + loadq + 10000 + 1 +  0 storeb // null terminator

0 // Loop over lines
while dup mem 9900 + loadq < do
  // Load Pattern
  mem loadb 1 << mem 1 + loadb or
  // Loop over columns, shift pattern
  mem 9900 + loadq 2 -
  while dup 3 > do
    1 -
    // Pattern to top of stack, ((pattern << 1) && 7)
  	swap 1 << 7 and
	// Copy index to top of stack, load value at memory address + index
	over mem + loadb or
	// Duplicate index + pattern
	twodup
	// ((110 >> pattern) && 1)
	110 swap >> 1 and
	// Swap duped index and pattern
	swap
	// Write new pattern to memory
	mem + swap storeb
	// Swap pattern and index for loop increment
	swap
  endwhile
  drop drop

  0 // Loop over columns, construct string from pattern at mem[10000]
  while dup mem 9900 + loadq < do
    // Test pattern to set current character to write to string.
    dup mem + loadb if
	  // Load a '*' into current character within string memory
	  dup mem + 10000 + 42 storeb
	else
	  // Load a ' ' into current character within string memory
	  dup mem + 10000 + 32 storeb
	endif

    1 +
  endwhile
  drop

  // Print constructed string
  mem 10000 + dump_s
  
  // Increment line counter
  1 +
endwhile
drop