900 "TAPELEN" store


##First, read in the source

# ""
# 1 while
# 	getline
# 	dup -1 = if
# 		pop
# 		0
# 	else
# 		"\n" swap + +
# 		1
# 	end
# end
# strlen 1 swap substr swap pop
# #bottom of stack now contains 1 string, the source code
# strlen "len" store
# "code" store

argc 1 = ! if
	"Please give the brainfuck file as a command-line argument." print lf
	exit
end
0 argvget "r" fopen "filehandle" store
""
filehandle fgetc
dup -1 = ! while
	+
	filehandle fgetc
dup -1 = ! end
pop
strlen "len" store
"code" store



##Then, create the tape
TAPELEN
dup 0 > while
	0 swap
1 - dup 0 > end



##Finally, start executing

@defun "execute" {
	#"start of 'execute': " print stackdump

	depth 1 + "depth" store

	#"trying to execute " print dup print lf

	"code" depth + store

	0 "i" store
	i len < while
		#"i = " print i print lf
		"code" depth + dup swapoutvar
		i stridx "c" store
		swap store  #uses the dupped name before the matching swapoutvar
		#"c = " c + print stackdump

		c "#" = if stackdump end
		c "+" = if 1 + 256 % end
		c "-" = if 255 + 256 % end
		c "." = if dup chr print end
		c "," = if
			pop
			getc
			dup -1 = if
				pop 255
			else
				ord 256 %
			end
			#{}"Input put on stack " print dup print lf
		end
		c ">" = if -1 roll end
		c "<" = if 1 roll end
		c "]" = if
			i "loopend" depth 1 - + store
			len "i" store  # == break
		end
		c "[" = if
			i "loopstart" depth + store
			#"loopstart" print depth print " = " print "loopstart" depth + get print lf
			0 "didloop" depth + store
			dup while
				1 "didloop" depth + store
				"code" depth + swapoutvar i 1 + len substr swap "code" depth + store execute
				#stackdump "i = " print i print lf
				"loopstart" depth + get "i" store
			dup end
			"didloop" depth + get ! if
				1 "searchdepth" store
				i 1 + "i" store
				"code" depth + dup swapoutvar
				i len < searchdepth 0 > * while
					i stridx "c" store
					#"Searching index " print i print " (char " print c print ")" print lf
					c "[" = if searchdepth 1 + "searchdepth" store end
					c "]" = if searchdepth 1 - "searchdepth" store end
					i 1 + "i" store
				i len < searchdepth 0 > * end
				#stackdump
				swap store
				searchdepth 0 = ! if
					"No matching ']' found for '[' at index " print loopstart print lf
					exit
				end
				i 1 - "i" store
			else
				"loopend" depth + get 1 + "loopstart" depth + get + "i" store
			end
			#"after loop, i = " print i print lf
		end

		i 1 + "i" store
	i len < end

	depth 1 - "depth" store
}

0 "depth" store

"code" swapoutvar
execute  #kaboom

depth 0 = ! if
	"The interpreter exited in depth " depth + "..." + print
end