Thread by @PgwadaS

(79/n) Day79
#Haskell
#CardanoCommunity
Restarting 1tweet/day

Thunks: used to represent code that should be execute to evaluate expression

Main feature of thunk is ability to b updated when their value is evaluated

https://twitter.com/PgwadaS/status/1472986659859755008

(80/n) Day80
#CardanoCommunity
instead of quote tweet, i will be using tweet thread from today

#Haskell laziness boils down to creating Thunk

Today we will look at how a Thunk is evaluated
let x = a+2 in ...

Fig shows how 3 stages are involved in evaluating x

(81/n) Day81
#CardanoCommunity
#Haskell

We say a value is unevaluated if its represented by thunk
We say a value is fully norm if its evaluated
Figure shows this

tomorrow we will look at weak head normal form(WHNF)

(82/n) Day82
#CardanoCommunity
#Haskell

We say that a value is weak head normal form (WHNF) if its represented by a closure corresponding to a data constructor

(83/n) Day83
#CardanoCommunity
#Haskell has lifted and unlifted types
This affects how memory is used
Lets first understand this
A type is lifted if its values may take special value "undefined" (bottom)
Most types are lifted due to thunks

84/n)Day84
#CardnaoCommunity
#Haskell has another concept "strictness" which affects runtime memory
A 1-arg function f is called strict, if given bottom val as arg, it returns bottom
Bottom is either "undefined" or forever loop

whether a func is strict depends on how arg is used