use strict;
# driveBase drives single tokens to baseform.  Its returned value is
# true for success.  It will always inscribe $wordCache{tok}{group} if
# it isn't already done.

sub driveBase{
    my($tok, $Args) =@_;
    return $wordCache{$tok} if $wordCache{$tok}{inscript};
    my $checkPrefix  # Check the prefix unless explicitly told not to.
        = defined($Args->{checkPrefix}) ? $Args->{checkPrefix} : 1;  
    my $skipPrefix = ! $checkPrefix;
    my($base,$atail,$ntail) = &split_token($tok); 
    my($sing, $unprefBase, $savgrp, $savbase);
    if($atail and $ntail ne ''){       # If there's both an atail and an ntail.
        &driveBase("$base,$atail", $Args);   # The base,tail can be a different group than the base.
        &equivWord($tok, "$base,$atail", 
                   {ntail => $ntail})}        # Treat GYROSCOPE,CONTROL MOMENT,3 same as GYROSCOPE,CONTROL MOMENT
   #  Assume that if $wordCache{$base,,$ntail}{group}, it's the same as $wordCache{$base}{group}
    # E.g. if SOFTGOODS LAB is a type of LAB, then it has the same group as LAB, unless we're told otherwise.
    elsif(!$atail and $ntail ne ''){          # Has a numeric tail but no alpha tail.
        &driveBase($base, $Args);
        &equivWord($tok, $base,
                   {ntail => $ntail})}
    elsif($wordCache{$base} and $wordCache{$base}{group}
          and $wordCache{$base}{group} ne 'UNKNOWN'
          and $base ne $tok){
        unless(member($wordCache{$base}{group}, qw(TIMEPERIOD PARTNO RANGE EXTENSION))
               or  $Args -> {nocomplain}){
            warn_once('driveBase', "WordCache should have been filled in when we asserted '$atail' isa type of '$base' ")};
        &equivWord($tok, $base, {atail => $atail});
        1}
    elsif(not ($atail eq '' and $ntail eq '')){  # There's either an atail or ntail but the form hasn't been seen before.
        &driveBase($base, $Args);
        &equivWord($tok, $base, {atail =>$atail, ntail=>$ntail})}
    elsif($checkPrefix and          # This is the main check for prefixed forms
          &is_prefixed_partspeechAnnotated($base)){  # wordCache{base} gets filled in.
        unless($tok eq $base){      #$prefixLessFm Mostly, base WILL eq tok, but catch the odd case.
            &equivWord($tok, $base, {atail => $atail})};
        1}
    # If $checkPrefix is false, then we've already stripped a prefix, 
    #  so it can't be an abbreviation, a number or an uncannical form.
    elsif($checkPrefix and $canon{$tok} and $canon{$tok} ne $tok){ 
        &driveBase($canon{$tok}, {%$Args, checkPrefix=>0});
        &equivWord($tok, $canon{$tok}, {})}
    elsif(($sing) = $tok =~ /(.+)S$/ and $canon{$sing} and $canon{$sing} ne $tok){  # So REQTS => REQT => REQUIREMENT
            &equivWord($tok, $canon{$sing}, {plural=>1})}
    elsif($checkPrefix and $abbrev{$tok}){    # Not normally invoked, as abbrevs have already been expanded usually.
        &equivWord($tok, $abbrev{$tok}, {abbreviation =>1})}
    elsif($checkPrefix and 
          (&part_number_p($base) or $atail eq 'PARTNO')){
        # P/N and PN: <partno> get transformed in immediate_transforms; see the improves file
        &baseInscript($tok, {group => 'PARTNO', 
                             root => $tok})}
    elsif($checkPrefix and &power_loc_p($tok)){
        &baseInscript($tok, {group => 'POWERLOC', root => $tok})}
    elsif($checkPrefix and &is_loc_code($tok)){
        &baseInscript($tok, {group =>  'LOC_CODE', root => $tok})}
    elsif($checkPrefix and $savbase = &is_measure_physics_frac($tok)){
        $num_item{$tok} = 1 unless defined($num_item{$tok});
        &baseInscript($tok, {group => $savbase,
                             num_item =>1, 
                             root => $tok})}
    elsif($savbase = &is_gerund($base, 1)){
        warn_once('GroupOf2', "Gerund $tok with base $base and tails '$atail', '$ntail'")
            if $atail or $ntail;
        &equivWord($tok, $savbase, {group=> 'GERUND',
                                    atail => $atail})}
    elsif($savbase = &is_pastverb($base, 1)){
        &equivWord($tok, $savbase, {group=> 'VERB',  # Even if the baseform is NVRB.
                                    atail => $atail,
                                    verbtense => 'PAST'})}
    elsif(&is_prefixed_verb($base, 1)){
        warn_once('GroupOf2.b', "Why wasn't $base of $tok found earlier?")}
    elsif($savbase = &is_ize_verb($base, 1)){
        &driveBase($savbase, {checkPrefix => 0});    # usually a no-op, but every once in a while...
        &equivWord($tok, $savbase, {group=> 'VERB',  # Even if the baseform is NVRB.
                                    atail => $atail})}
    elsif($sing = &is_3rdpersonverb($base, 1)){     # BOXES Could be either the plural or the 3rd person sing.
        &equivWord($tok, $sing, {s_ending => 1,
                                 atail => $atail})}
    elsif($savbase = &is_derived_noun($base, 1)){  # '-TION' words etc., REFUSAL, REBUTTAL, GOODNESS, BUSINESS
        &equivWord($tok, $savbase, {group => 'NOUN',  # A few NVRBS like POSITION and CONDITION will be called out explicitly.
                                    atail => $atail},
                   {no_use =>[qw(actorform)]})}
    elsif($savbase = &is_derived_adj($base, 1)){
        &equivWord($tok, $savbase, {group =>         'ADJECTIVE', 
                                    atail => $atail},
                   {no_use =>[qw(actorform)]})}
    elsif($savbase = &is_adverb($base, 1)){
        &equivWord($tok, $savbase, {group => 'ADVB',  
                                    atail => $atail})}
    elsif($types{$base}){                # presumably this token will get gobbled
        warn_once('GroupOf2.c',         # by one of the neighboring tokens.
                  "Why does modifier $base have a tail $atail") if $atail;
        &baseInscript($tok, {group =>  'MODIFIER', root => $tok})}         
    elsif($sing = &singularOfNoun($tok, 1)){
        &equivWord($tok, $sing, {plural=>1})}
    elsif($base =~ /^[a-z,A-Z]$/){        
        &baseInscript($tok, {group =>  'LETTER', root => $tok})}
    # if $checkPrefix is false, then we've already stripped a prefix off the tok, so it can't be a roman numeral
    elsif($checkPrefix and (&number_p($tok) or &roman_number_p($tok))){
        &baseInscript($tok, {group => 'NUMBER', root => $tok})}
    elsif(is_alphnum($base)){
        &baseInscript($tok, {group => 'ALPHNUM', root => $tok})}
    elsif($base =~ /^$punctuation_tokens$/){
        &baseInscript($tok, {group => 'PUNCTUATION', root => $tok})}
    # So COUNTERDOFFABLE gets tested as DOFFABLE and returns ADJECTIVE
    elsif($checkPrefix and 
          $unprefBase and         # Set in an earlier test, above
          $savgrp = &group_of($unprefBase, 1) and  # This time, try to derive a group for the base.
          &member($metagroup{$savgrp}, 'NVRB', 'NOUN','VERB','ADJECTIVE','ADVB', 'GERUND')){}
    else{
        &baseInscript($tok, {group => 'UNKNOWN', root => $tok})};
    $wordCache{$tok}}