# euclid.eas - highest common factor
# SCCSID("@(#)/export/home/staff/mike/src/language/eta/easpit/SCCS/s.euclid.eas	1.1")
#
#   ###	NOT FINISHED

# This is a function of two arguments, so if the caller adheres to the
# standard calling convention, the stack at the point of our first
# instruction will be: a b addr.

# Prologue: roll addr under arguments
>EUCLID: N2 H N2 H				# (... addr) a b

# Body of loop
>EUCLIDloop: N0 H				# a b b
A N0 N1 S S T		# (skip if not done)	# a b
N1 N<EUCLIDdone T	# (jump to end)		# a b(=0)
N0 N1 S H					# a b a
E						# a b/a b%a
N0 N2 H T					# a b%a		# discard b/a
N1 H						# b%a a
N1 N<EUCLIDloop T

# Epilogue: discard junk, roll addr above return value
>EUCLIDdone: N0 T				# (... addr) a
N1 N2 H						# ... a 1 addr
T