del_ch(STRING,CHAR) -(i,i)
del_ch/2 deletes all occurrences of a character(arg.2) in a string(arg.1),"destructively" (i.e. it permanently alters the string(arg.1).
del_ch(STRING,CHAR,STRING) -(i,i,o)
del_ch/3 deletes all occurrences of a character(arg.2) in a string(arg.1), and preserves the string as it is, copying the result to an output-string(arg.3).
This family of predicates has been implemented in Pure 32-bit Assembly.