algebrite

# If the number of args is odd then the last arg is the default result. Eval_test = -> orig = p1 p1 = cdr(p1) while (iscons(p1)) # odd number of parameters means that the # last argument becomes the default case # i.e. the one without a test. if (cdr(p1) == symbol(NIL)) push(car(p1)); # default case Eval() return # load the next test and eval it push(car(p1)) Eval_predicate() p2 = pop() if isone(p2) # test succesful, we found out output push(cadr(p1)) Eval() return else if !iszero(p2) # we couldn't determine the result # of a test. This means we can't conclude # anything about the result of the # overall test, so we must bail # with the unevalled test push orig return # test unsuccessful, continue to the # next pair of test,value p1 = cddr(p1) # no test matched and there was no # catch-all case, so we return zero. push_integer 0 # we test A==B by first subtracting and checking if we symbolically # get zero. If not, we evaluate to float and check if we get a zero. # If we get another NUMBER then we know they are different. # If we get something else, then we don't know and we return the # unaveluated test, which is the same as saying "maybe". Eval_testeq = -> # first try without simplifyng both sides orig = p1 push(cadr(p1)) Eval() push(caddr(p1)) Eval() subtract() subtractionResult = pop() if (iszero(subtractionResult)) p1 = subtractionResult push_integer(1) else # they don't seem equal but # let's try again after doing # a simplification on both sides push(cadr(p1)) Eval() simplify() push(caddr(p1)) Eval() simplify() subtract() p1 = pop() if (iszero(p1)) # if we get symbolically to a zero # then we have perfect equivalence. push_integer(1) else # let's try to evaluate to a float push p1 yyfloat() p1 = pop() if (iszero(p1)) # if we got to zero then fine push_integer(1) else if isnum(p1) # if we got to any other number then # we know they are different push_integer(0) else # if we didn't get to a number then we # don't know whether the quantities are # different so do nothing push orig # Relational operators expect a numeric result for operand difference. Eval_testge = -> orig = p1 comparison = cmp_args() if !comparison? push orig return if ( comparison >= 0) push_integer(1) else push_integer(0) Eval_testgt = -> orig = p1 comparison = cmp_args() if !comparison? push orig return if ( comparison > 0) push_integer(1) else push_integer(0) Eval_testle = -> orig = p1 comparison = cmp_args() if !comparison? push orig return if ( comparison <= 0) push_integer(1) else push_integer(0) Eval_testlt = -> orig = p1 comparison = cmp_args() if !comparison? push orig return if ( comparison < 0) push_integer(1) else push_integer(0) # not definition Eval_not = -> push(cadr(p1)) Eval_predicate() p1 = pop() if (iszero(p1)) push_integer(1) else push_integer(0) ### and ===================================================================== Tags ---- scripting, JS, internal, treenode, general concept Parameters ---------- a,b,... General description ------------------- Logical-and of predicate expressions. ### # and definition Eval_and = -> p1 = cdr(p1) while (iscons(p1)) push(car(p1)) Eval_predicate() p2 = pop() if (iszero(p2)) push_integer(0) return p1 = cdr(p1) push_integer(1) # or definition Eval_or = -> p1 = cdr(p1) while (iscons(p1)) push(car(p1)) Eval_predicate() p2 = pop() if (!iszero(p2)) push_integer(1) return p1 = cdr(p1) push_integer(0) # use subtract for cases like A < A + 1 # TODO you could be smarter here and # simplify both sides only in the case # of "relational operator: cannot determine..." # a bit like we do in Eval_testeq cmp_args = -> t = 0 push(cadr(p1)) Eval() simplify() push(caddr(p1)) Eval() simplify() subtract() p1 = pop() # try floating point if necessary if (p1.k != NUM && p1.k != DOUBLE) push(p1) yyfloat() Eval() p1 = pop() if (iszero(p1)) return 0 switch (p1.k) when NUM if (MSIGN(p1.q.a) == -1) t = -1 else t = 1 when DOUBLE if (p1.d < 0.0) t = -1 else t = 1 else t = null return t