\nAn interesting aspect of every computer language is what it thinks of as “true” vs “false”. Many languages think 0 is false, while any other declared value, such as “hello” or even -1, is true. JavaScript, for instance, seems to see it that way, in my experience.<\/p>\n
Note herein the difference between 0 (zero) and () (empty brackets), since they may look almost the same on some browsers.<\/em><\/p>\n \nLISP, however, seems to see it differently: anything defined as something other than nil or () is true, even if it’s defined as 0. LISP doesn’t have false; just nil. The only way to attain nil value is to be declared nil or () or else to arrive there by calculation.<\/p>\n In LISP, as in some other computer languages, an undefined (or undeclared) variable isn’t nil (or false); rather, the interpreter will complain when it encounters one.<\/p>\n So, a main thought: in LISP, (or 0 1) evaluates to 0, which is “not false”. However, (or nil) evaluates to nil, which is false, in LISP.<\/p>\n Surprising, eh?<\/p>\n Source:<\/p>\n cs.cmu.edu<\/a><\/p>\nJack of Oracle Tutoring by Jack and Diane,<\/a> Campbell River, BC.\n","protected":false},"excerpt":{"rendered":" Self-tutoring about Comp Sci: the tutor mentions true and false in LISP. An interesting aspect of every computer language is what it thinks of as “true” vs “false”. Many languages think 0 is false, while any other declared value, such …<\/p>\n