Что делает эта программа, и какие у нее входные данные?

DOMAINS 
variable=STRING 
coefficient=INTEGER 
vars=s(variable,coefficient) 
varlist=vars* 
PREDICATES 
collect(STRING,STRING) 
accumulate(STRING,varlist,varlist) 
addnextvar(STRING,varlist,STRING,varlist) 
getcoeff(STRING,coefficient,STRING) 
strtoint(STRING,INTEGER) 
getnumstr(STRING,STRING,STRING,STRING) 
getvarname(variable,STRING,variable,STRING) 
addvar(variable,coefficient,varlist,varlist) 
getrez(varlist,STRING) 
getresult(STRING,varlist,STRING) 
start 
CLAUSES 
collect(STR,RESULT) :- 
accumulate(STR,[],REZLIST), 
getrez(REZLIST,RESULT). 
accumulate(STR,VLIST,REZLIST) :- 
STR_LEN(STR,0), 
REZLIST=VLIST. 
accumulate(STR,VLIST,REZLIST) :- 
addnextvar(STR,VLIST,OSTATOK,NEWLIST), 
accumulate(OSTATOK,NEWLIST,REZLIST). 
addnextvar(STR,VLIST,OSTATOK,NEWLIST) :- 
getcoeff(STR,COEFF,OST1), 
getvarname("",OST1,VARNAME,OSTATOK), 
addvar(VARNAME,COEFF,VLIST,NEWLIST). 
getcoeff(STR,COEFF,OSTATOK) :- 
FRONTCHAR(STR,'+',OST), 
getnumstr("",OST,COEFFSTR,OSTATOK), 
strtoint(COEFFSTR,COEFF). 
getcoeff(STR,COEFF,OSTATOK) :- 
FRONTCHAR(STR,'-',OST), 
getnumstr("",OST,COEFFSTR,OSTATOK), 
strtoint(COEFFSTR,CF), 
COEFF=-CF. 
getcoeff(STR,COEFF,OSTATOK) :- 
getnumstr("",STR,COEFFSTR,OSTATOK), 
strtoint(COEFFSTR,COEFF). 
strtoint(STR,1) :- 
STR_LEN(STR,0). 
strtoint(STR,INT) :- 
STR_INT(STR,INT). 
getnumstr(S1,STR,COEFFSTR,OSTATOK) :- 
STR_LEN(STR,0), 
COEFFSTR=S1, 
OSTATOK=STR. 
getnumstr(S1,STR,COEFFSTR,OSTATOK) :- 
FRONTCHAR(STR,'+',_), 
COEFFSTR=S1, 
OSTATOK=STR. 
getnumstr(S1,STR,COEFFSTR,OSTATOK) :- 
FRONTCHAR(STR,'-',_), 
COEFFSTR=S1, 
OSTATOK=STR. 
getnumstr(S1,STR,COEFFSTR,OSTATOK) :- 
FRONTCHAR(STR,C,_), 
C>'9', 
COEFFSTR=S1, 
OSTATOK=STR. 
getnumstr(S1,STR,COEFFSTR,OSTATOK) :- 
FRONTCHAR(STR,C,_), 
C<'0', 
COEFFSTR=S1, 
OSTATOK=STR. 
getnumstr(S1,STR,COEFFSTR,OSTATOK) :- 
FRONTCHAR(STR,C,OST), 
STR_CHAR(S2,C), 
CONCAT(S1,S2,ST), 
getnumstr(ST,OST,COEFFSTR,OSTATOK). 
getvarname(S1,STR,VARNAME,OSTATOK) :- 
FRONTCHAR(STR,'+',_), 
VARNAME=S1, 
OSTATOK=STR. 
getvarname(S1,STR,VARNAME,OSTATOK) :- 
FRONTCHAR(STR,'-',_), 
VARNAME=S1, 
OSTATOK=STR. 
getvarname(S1,STR,VARNAME,OSTATOK) :- 
STR_LEN(STR,0), 
VARNAME=S1, 
OSTATOK=STR. 
getvarname(S1,STR,VARNAME,OSTATOK) :- 
FRONTCHAR(STR,C,OST), 
STR_CHAR(S2,C), 
CONCAT(S1,S2,ST), 
getvarname(ST,OST,VARNAME,OSTATOK). 
addvar(VARNAME,COEFF,[],[NEWTAIL]) :- 
NEWTAIL=s(VARNAME,COEFF). 
addvar(VARNAME,COEFF,[s(VARNAME,COEFFICIENT)|T],[s(VARNAME,SUMMA)|T]) :- 
SUMMA=COEFFICIENT+COEFF. 
addvar(VARNAME,COEFF,[H|T],[H|NEWTAIL]) :- 
addvar(VARNAME,COEFF,T,NEWTAIL). 
getrez([],"0"). 
getrez([s(VARNAME,COEFF)|T],RESULT) :- 
COEFF>0, 
STR_INT(S1,COEFF), 
CONCAT(S1,VARNAME,S2), 
getresult(S2,T,RESULT). 
getrez([s(VARNAME,COEFF)|T],RESULT) :- 
COEFF<0, 
STR_INT(S1,COEFF), 
CONCAT(S1,VARNAME,S2), 
getresult(S2,T,RESULT). 
getrez([s(_,0)|T],RESULT) :- 
getrez(T,RESULT). 
getresult(STR,[],RESULT) :- 
RESULT=STR. 
getresult(STR,[s(VARNAME,COEFF)|T],RESULT) :- 
COEFF>0, 
CONCAT(STR,"+",S1), 
STR_INT(S2,COEFF), 
CONCAT(S1,S2,S3), 
CONCAT(S3,VARNAME,S), 
getresult(S,T,RESULT). 
getresult(STR,[s(VARNAME,COEFF)|T],RESULT) :- 
COEFF<0, 
STR_INT(S2,COEFF), 
CONCAT(STR,S2,S3), 
CONCAT(S3,VARNAME,S), 
getresult(S,T,RESULT). 
getresult(STR,[s(_,0)|T],RESULT) :- 
getresult(STR,T,RESULT). 
 
 
start :- 
WRITE("‚ўҐ¤ЁвҐ, Ї®¦ «г©бв , ў иҐ ўла ¦Ґ ЁҐ:"), 
NL, 
READLN(STR), 
NL, 
collect(STR,RESULT), 
 
WRITE("ђҐ§г«мв в:"), 
NL, 
WRITE(RESULT), 
NL, 
NL. 
 
 
GOAL 
start