Menu
How is it that in line below on the right side of equation one could use symbol 'fibs' although it is not yet definied:
let fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
495
Is there any symbol for representing it? It is common to write "DNE" for "does not exist". My preferred symbol is not to write undefined things, the empty symbol.
Symbols facilitate understanding of the world in which we live, thus serving as the grounds upon which we make judgments. In this way, people use symbols not only to make sense of the world around them, but also to identify and cooperate in society through constitutive rhetoric.
System symbols are elements that allow systems to share parmlib definitions while retaining unique values in those definitions. System symbols act like variables in a program; they can take on different values, based on the input to the program.
The point is that the definition of fibs
fibs = 0 : 1 : zipWith (+) fibs (tail fibs)
is not evaluated until it is used somewhere else. Then the definition unfolds using the already known part. We begin with fibs = 0 : 1 : ???. Then if the third element is ever needed, the definition is evaluated one step further,
fibs = 0 : 1 : zipWith (+) (0 : 1 : ???) (tail (0 : 1 : ???))
= 0 : 1 : zipWith (+) (0 : 1 : ???) (1 : ???)
= 0 : 1 : (0 + 1) : zipWith (+) (1 : ???) (???)
but then the unknown part ??? has become partly known, it has been determined to be ??? = 1 : ????, so the unfolding can go on,
= 0 : 1 : 1 : zipWith (+) (1 : 1 : ????) (1 : ????)
= 0 : 1 : 1 : 2 : zipWith (+) (1 : ????) (????)
-- now ???? is known to be 2:?????
= 0 : 1 : 1 : 2 : zipWith (+) (1 : 2 : ?????) (2 : ?????)
etc.
133
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
