extracts the first prolog token in front of a string
prologtoken("Hello World",Token,RestString)
prologtoken(String,Token,RestString) (i,x,x)
string(String) (i) string to be separated
string(Token) (x) first prolog token contained in String
string(RestString) (x) String without its leading white spaces characters and
Token
Prologtoken() skips all white space characters (blanks,tabs) and separates from the resulting string the first valid prolog token. The remainder is matched with RestString. A valid prolog token is either a variable, an atom or string, an integer, a character, brackets, dots, etc.
readln(Input), % e.g. enter "3+5", "4*6" prologtoken(Input,T1,,R1), prologtoken(R1,Op,T2), str_int(T1,I1),str_int(T2,I2), Expr =.. [Op,I1,I2],e Sum is Expr, write(Sum),nl.
A runtime error occurs if the arguments belong to the wrong domain.
prolog-process, client-server, object
frontchar , str_char , frontchar ,
fronttoken , concat , str_len