Now consider "2,1,LE". This RPN expression could be read as "is
two less than or equal to one?". The natural response is "no"
-and thus the RPN expression 2,1,LE evaluates to 0.
+and thus the RPN expression 2,1,LE evaluates to 0.
=head1 Reading the IF Operator
1) 20,10,GT,10,20,IF eval is 20,10,GT = 1 result is 1,10,20,IF
read the eval as pop "20 is greater than 10" so push 1
-
+
2) 1,10,20,IF eval is 1,10,20,IF = 10 result is 10
read pop "if 1 then 10 else 20" so push 10. Only 10 is left so
Read eval as "if input > 10 then true" and replace "input,10,GT"
with "A":
-
+
2) A,10,input,IF eval is A,10,input,IF
read "if A then 10 else input". Now replace A with it's verbose
Answer 1:
3*2+1 = 7 and 3*(2+1) = 9. These expressions have
- different answers because the altering of the plus and
+ different answers because the altering of the plus and
times operators alter the order of their evaluation.