when/case + general cleanup

[drkameleon]

Description

Continuing from here: #1653

Type of change

• Code cleanup
• Enhancement (implementation update, or general performance enhancements)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (documentation-related additions)

[drkameleon]

Final version

(nothing written in stone; but to avoid going over it till the end of time and not merging it, let's merge it and we can change it as we go, if we need to do so. also, the approach is quite simplistic, less intrusive than initially designed, so that we don't overcomplicate things too much too soon; we have all the time in the world for that... lol)

case

match given argument against different values and execute corresponding block

x: 2

; the main block is always evaluated!
case x [
    1   -> print "x is one!"
    2   -> print "x is two!"
    any -> print "x is none of the above"
]
; x is two!

key: "one"
case key [
    "one" 1,        ; we can also return
    "two" 2         ; simple constant values directly
]
; => 2

case "hello" #[
    hello: "hola"
    adios: "goodbye"
]
; => "hola"

when

check conditions one by one and execute corresponding block accordingly

; the main block is always evaluated!
when [
    prime? 4 -> print "yes, 4 is prime - wait, what?!"
    prime? 5 -> print "yes, 5 is prime
    prime? 7 -> print "yes, 7 is prime
    true     -> print "none of the above was true"
]
; yes, 5 is prime

when.any [
    prime? 4 -> print "yes, 4 is prime - wait, what?!"
    prime? 5 -> print "yes, 5 is prime"
    prime? 7 -> print "yes, 7 is prime"
]
; yes, 5 is prime
; yes, 7 is prime

x: 2
when.has: x [
    [=0] -> print "x is zero!"
    [<1] -> print "x is less than 1"
    [<4] -> print "x is less than 4"
    true -> print "x is >= 4"
]
; x is less than 4

[drkameleon]

And...
ready to merge! 🚀