Coming from elm to haskell

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#1

First impressions…
Surprised finding so much similar things in haskell and elm.
On the other hand, annoyed about some differences
Example functions for integer divisions
in Elm 7 // 3 == 2 missing in Haskell, in Haskell divide 7 3 missing in Elm
floor (7 / 3) same in Elm and Haskell
I was translating one of my elm programs to haskell, namely the function of Julian Date JDN calculated from the given date. See my elm code function jdnGr

I should add lots of parentheses changing all ( x // y ) in elm to (divide x y) in haskell
Well, I found just a haskell package containing julian date in the date.time library.
Next I should learn, how to use it as imported to my code.

I like a lot haskell utility ghci with handy features, elm repl is comparable tool.
I miss anyway in haskell a dev tool similar to elm reactor.

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#2

If you miss some operator you’re used to, you can always declare it yourself:

(//) :: Integral a => a -> a -> a
(//) = div
infixl 7  //

you can also use functions infix, like

7 `div` 3 == div 7 3

Note that if not explicitly declared, infix-used functions have fixity 9. Luckily, in GHC.Real, we have the following fixity declaration:

infixl 7  /, `quot`, `rem`, `div`, `mod`
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#3

Here is my very first haskell module and the main which calculate Julian Day Number (needed in many astronomical calculations).

I have declared there operator ‘//’ with infixl.

I don’t understand the meaning of the number 7 argument of infixl, just realised only that changing the value too low will show incorrect result values.

#4

There’s a good explanation in this section of an archive of Stack Overflow documentation.

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#5

Yes, really well explained the binding precedence of operators vs functions.
Wise use of infixes can reduce parentheses.