06:24 <gl> 'lo

17:53 <keithr2> I began reading a book last night - "A Functional Approach to Programming" -- I am trying to understand what is functional programming. -- The book uses CAML -- I understood from my reading that one would like to avoid using assignment because correctness is sacrificed. (?) -- Anyway in the intro to CAML the author introduces variables and their declarations -- > let x = 2+3;; -- is that not an assignment?

17:53 <mrvn> No, thats a binding.

17:54 <kev> I take it by 'assignment' the term means functions with side effects?

17:54 <mrvn> let x = 7 let _ = let x = 7 in x let _ print_int x;;

17:55 <mrvn> s/print/= print/

17:55 <mrvn> assignment is a sideeffekt.

17:56 <MegaWatS> keithr: no binding works more like constant assignment

17:56 <mrvn> Assignment would mean that you assign a new value to the old x.

17:56 <MegaWatS> when you "re-assign", you only shadow out the old value

17:56 <kev> okay, so I have absolutely no clue how to parse that ;)

17:56 <MegaWatS> i.e.

17:56 <MegaWatS> let x = 2

17:56 <MegaWatS> and then late

17:56 <MegaWatS> let x = 3

17:56 <MegaWatS> is more like

17:56 <MegaWatS> const x = 2; foo() { const x = 3; ... }

17:56 <MegaWatS> than like

17:56 <MegaWatS> int x = 2; foo() { x = 3; ... }

17:57 <MegaWatS> ie the old binding still exists - you can`t change it`s value - you only shadowed it out of the current namespace

18:00 <mrvn> The main thing is probably that you know that nothing will change your varibale no matter what function you call. You can only change it yourself by shadowing it with a new one.

18:01 <mrvn> Makes it possible to proff something works without looking at all the functions it calls closelz.

18:03 <mrvn> mep: The one you intend to use.

18:03 <mrvn> Try libglib2.0-dev.

18:04 <mrvn> ups

18:15 <keithr2> ok -- a binding is not an assignment -- let x = 2+3;; is a binding -- I can create another binding > let x = 5+6;; but the x is not the same variable ( provided I used the right structure) -- that is one would never see those two expressions within the same block of code -- correct?

18:17 <MegaWatS> why not? you can shadow it in the same block of code

18:18 <MegaWatS> look at the following piece of C++ code:

18:18 <MegaWatS> for(;;) { const x = 3; int y; { const x = 4; y = x; } cout << x << " " << y; }

18:19 <MegaWatS> which is different from for(;;) { int x = 3; int y; x = 4; y = x; cout << x << " " << y; }

18:20 <MegaWatS> or especially the difference between the following two: int x = 2; for(;;) { x = x + 1; if(x >= 10) break; } and const x = 2; for(;;) { int y = x + 1; const x = y; if(x >= 10) break; }

18:20 <MegaWatS> so you CAN have two let bindings to the same variable in the same block

18:20 <MegaWatS> they will shadow each other: let x = 2 in let x = 3 in [... ]

18:21 <MegaWatS> you can even do let x = 2 in let x = x + 1 in

18:21 <MegaWatS> as the expression on the RHS can refer to the old value

18:21 <keithr2> :) ok

18:21 <MegaWatS> but each let binding creates a new variable with a new scope

18:22 <MegaWatS> ie let ... is like { const ... = ...; ... } , including the braces - it automatically already creates the new scope

18:23 <keithr2> thanks