The pile of feature information that used to be here is now 
updated in the spreadsheet "Features.xls".

MACREL has been identified as "the assembler to beat".  It 
has enough features to just about do what we need, and obeys 
the PDP-8 conventions sufficiently to assemble the existing 
body of PDP-8 code, as well.

SMAL8 is currently missing EXPUNGE, FIXMRI, and FIXTAB, which 
are pretty essential for assembling legacy code without modification.

Also critical for legacy code would be literal support.

Most of the other PAL variants come pretty easily after that.

MACREL is not entirely compatible with MACRO-8, so probably 
both feature sets would need to be implemented.  The MACREL 
relocation model is also page-oriented -- things can go on 
any page, but allocate the whole page.  That "solves" the 
page packing problem, but I'd like to hope to do better.

The SABR assembler is interesting, but doesn't support enough 
of the directives used in legacy code.  It also has it's own 
assembler hacks and funky runtime to support a coding model 
that pretends to be independent of the addressing limitations 
of the PDP-8.

The RALF assembler is even worse, and barely supports the 
PDP-8 at all.  It is more properly described as an assembler 
for the Floating Point Processor.  That was good enough for 
Fortran IV, and would probably support C as well, if I wanted 
to target Small-C for the FPP.

Features we still need:
START, not S
Fix TEXT compatibility.
DEVICE pseudo-op
FILENAME pseudo-op
BSW
DVI/NMI/SHL/ASR/LSR
MQL/MQA/SWP/CAM/ACL
SKON/SRQ/GTF/RTF/SGT/CAF
KCF/KIE
IOT/OPR
PSF/PCF/PPC
PCE, RPE
TFL/TSK/SPF/SPI
EXPUNGE/FIXMRI/FIXTAB pseudo-ops
ASECT/DSECT/FSECT/RSECT/XSECT/ZSECT pseudo-ops
ENPUNCH/NOPUNCH pseudo-ops
GLOBAL/ENTRY/EXTERNAL/ZTERNAL/SECREF pseudo-ops
IFDEF/IFNDEF pseudo-ops
IFZERO/IFNZRO pseudo-ops
XLIST pseudo-op
Literals: "[", "("
Multiply with "^", divide with "%"
ZBLOCK pseudo-op

Features for later:
<> Expressions
^" for control characters
^B, ^D, ^O, trailing dot for radix control
backslash lexical operator
CHAIN as well as INCLUDE
Colon locals
CDI for CXF
DTORG?
FLD function
JSW
LEVEL
Links for offpage direct access
LIST/NOLIST
MEXIT
NARGS/NCHAR
Assembly time PUSH, POP
RADIX
RELOC
REPT/ENDR
Two character constants with single quote
Trailing $ for local symbols
VERSION
XEDF