Haskell like where clause for f-script functions

[siddhantk232]

A haskell function that uses where clause:

qsort1 []     = []
qsort1 (p:xs) = qsort1 lesser ++ [p] ++ qsort1 greater
    where
        lesser  = filter (< p) xs
        greater = filter (>= p) xs

Things to note:

• Haskell function body can only have a single expression

• Haskell also has a let ... in construct. The above code using let ... in would look like:

  qsort1 []     = []
  qsort1 (p:xs) = 
    let lesser  = filter (< p) xs
        greater = filter (>= p) xs
    in qsort1 lesser ++ [p] ++ qsort1 greater

This allows haskell programmers to organize their code that favors readability. If the function body derivation depends on something that should be important to the reader then let ... in is used. Otherwise, where clause is used to grab the reader's attention immediately to the function body.

We don't need let ... in syntax because f-script functions allow multiple expressions and one of which is variable definition:

-- string first-item():
list<string> items:

string item: items[0] ;; A variable definition before the main body
item ;; last expression is automatically returned

What about where? Let's try to fit it in:

-- string first():
list<string> items:

res

where {
  string res: items[0]
}

Where else can we use where?

[siddhantk232]

From @amitu:

I won’t mind a

— integer foo(): x + y
integer x:  ;; function argument

integer y: 20 ;; let clause / local variable

The caption like is the before where expression and the body is the where block.