<thomas001>
File "x.ml", line 10, characters 8-12:
<thomas001>
i started ocaml today,so i'm a total newbie
<gehel>
2s
<thomas001>
2s ?
<gehel>
2 sec
<thomas001>
oh,ok
<gehel>
ocamlopt thinks that you apply fib2 to n, 1, 1, _and_ printf "%i\n" fib 20
<gehel>
in fib2 n 1 1;; printf ...
<gehel>
do it
<gehel>
if you don't want to use ';;', ocamlopt knows that the def of a function is finished if he parse a new 'let'
<gehel>
so
<gehel>
let fib ....
<thomas001>
thx it compiles now
<gehel>
let _ = printf "%i\n" fib 20
<thomas001>
printf (fib 20) <-- had to be change to this
<gehel>
b
<thomas001>
b?
<gehel>
wrong buffer :)
<thomas001>
*g*
<thomas001>
thank you gehel for the help
<gehel>
you're welcome
<thomas001>
ocaml seems to be not very popular,isn't it ?
<gehel>
it depends where
<gehel>
i think his popularity is growing
<gehel>
in france, some people use/know it
<gehel>
it's a university language..
<thomas001>
i got to know it from the mldonkey source,it looked pretty interesting
<gehel>
it is :)
<thomas001>
cool i don't need fib and fib2 i can call fib2 fib
<thomas001>
nice scoping ;)
<thomas001>
can i write several commands after a in or only one ?
<gehel>
i don't understand
<thomas001>
sry bad english
<gehel>
oh, after "in a"
<gehel>
let a = 1 in (print_string "foo"; dummy(); a+1)
<thomas001>
parens must be ?
<thomas001>
print_string "foo";dummy();a+1;; <-- does this work ?
<gehel>
in fact, when you use a block ( parenthesis can be replaced by "begin/end", all the expression except the last must be unit
<gehel>
if dummy is : fun blabla -> unit, ocamlopt/ocamlc will accept
<gehel>
if not, you'll have a warning, iirc
<gehel>
if you don't use parens, 'a' will be defined only in the first expression, so 'a+1' is not defined
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<gehel>
(no parens, and no begin/end)
<gehel>
'let a = 1 in print_string "foo"; a' is wrong
<thomas001>
hmm..what is the difference between ; and ;; ?
<gehel>
use ; between instruction in the same function
<gehel>
;; when you end a function
<gehel>
;; is required when you call 'ocaml' in your shell
<gehel>
to ask an evaluation
<thomas001>
so ;; closes the innermost function definition ?
<gehel>
yes
<gehel>
in a file, you don't need it
<gehel>
a new let will suffice
<gehel>
let/type
<thomas001>
on toplevel does it matter if i use ; or ;; to seperate instructions ?
<gehel>
;; is the end of a function
<gehel>
; is the end of an instruction
<thomas001>
i replaced my printf:
<thomas001>
print_int (fib 20);;
<thomas001>
print_newline ();;
<gehel>
it's okay
<thomas001>
but with ; it works also
<thomas001>
so does not matter ?
<gehel>
it works, but the type is not the same
<gehel>
with ;, the type is the one of all the expression: print_int (); print_newline();;
<thomas001>
and with ;; ?
<gehel>
with ;;, the toplevel evalue the first and the second expression, and send a type for each
<thomas001>
ok,thank you a lot
<gehel>
np
<gehel>
thomas001 try with some function that don't do side effet.. like this: 1+2; 2+3;;
<gehel>
and this one is okay: ();1;; , because () has type unit
<thomas001>
oh really newbie question:what is a side effect ? (never encountered this term in C/C++)
<gehel>
when you print something, etc..
<gehel>
when you don't compute
<thomas001>
I/O ?
<gehel>
for example
<thomas001>
thx
<thomas001>
wow braindead ocaml book: let (+)=( * ) ;;
<gehel>
:)
<gehel>
operator redefinition
<gehel>
(+), like ( * _, like (-), is a function
<gehel>
1+2 == (+) 1 2
<gehel>
we don't use (*) cuz (* if a comment beginning
<thomas001>
works 1 bla 2 == (bla) 1 2 only on + - * / ?
<gehel>
i think
<gehel>
i think so
<gehel>
(and other arithmetic operators_
<gehel>
+. -. *. etc
<thomas001>
thx
<gehel>
let's go to bed now.. 2h40 am, and i must be at university this morning :/
<gehel>
good night
* gehel
&
<thomas001>
gn8
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<intero>
hi all
<gehel>
'lo
* intero
is away: I'll answer as I come back, I am away now, sorry =(
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<matkor>
Hellou :)
<docelic>
(: uolleH
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<matkor>
What type would act like Array but would allow to append new values ?
<whee>
a list?
<matkor>
whee: Yop. Might be :) thanks List in ocaml has constant time access to random element ?
<whee>
not constant time access
<whee>
you could use arrays and just resize if you require that
<matkor>
whee: yes, but I suspect that appending to array is costly (as it returns copy of array) So to do it efficient I would have to implement my type ...
<matkor>
Strange that ocaml doesn't have sth like C++ STL vectior<> .... ;)
<whee>
arrays are the same as vector
<whee>
I don't believe vectors automatically resize themselves either
<matkor>
whee: You mean ocaml vector nor C++ STL's vector<> ?
<vegai>
STL's vector is an array with a weird name, is it not?
<whee>
the STL vector and ocaml's Array module are essentially the same
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<sam_>
there's nothing strange that there'd be something missing in ocaml standard library, it's more like what you should expect :-)
<whee>
sam: it's still not really missing, though :P
<whee>
the STL vector is just a fancy api for arrays, which is what the Array module is'
<sam_>
whee, well, i don't know exactly what stl vectors are like. i guess i was expecting them to be similar to java vectors
<sam_>
as in, with support for mutable extension
<matkor>
STL vectors have constant time append elem , which seems not be case with ocaml's arrays (but it's not topic for me to discus as I'm starting to learn ocaml :) )
<whee>
matkor: I don't believe they do
<whee>
they're really just implemented with C arrays, which don't have the ability to be extended
<matkor>
whee: they do , it's in standard.
<whee>
they must not use C arrays, then :P
<sam_>
matkor, it is?
<whee>
which would imply that they aren't constant time access
<whee>
which they obviously are
<sam_>
matkor, memory block extension surely is in c standard, but array extension? you sure about that?
<matkor>
whee: They use. But they allocate twice big array as needed and copy elements to it. It's still constant time append.
<whee>
there's no appending going on
<whee>
most likely it mallocs double the array size and copies the memory
<whee>
which is far from an append
<sam_>
matkor, as far as i know, there is no array extension in c standard.. extension for dynamic allocated blocks, yes, but for staticly allocated blocks, no
<sam_>
and arrays can be in both
<whee>
looking at the source to ocaml's Array module, it's basically a direct interface to C arrays
<matkor>
sam_: You are right.
<matkor>
whee: And how big memory is allocated when append of element is made ? n+1 ?
<whee>
append?
<whee>
there is no appending with C style arrays
<matkor>
OK. Never mind. I will learn more and than I hope will be able to be more clearer ...
<sam_>
matkor, there is no appending one element.. there's appending of two arrays together, which will create an array of size of their sizes together
<sam_>
matkor, so, no. there is no 'vector' such as what you are looking for
<whee>
if you need to 'resize' you could use a reference to an array and make a new, larger array and blit the values over
<whee>
but most likely you'd be better off with a different data structure
<whee>
arrays don't have much use with a functional style
<sam_>
yes, ocaml has what you want, if you code it yourself
<sam_>
:-)
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<matkor>
How should I access object members ?
<matkor>
class myclass =
<matkor>
object
<matkor>
val mutable member = 3;
<matkor>
end;;
<matkor>
<matkor>
let m = new myclass;;
<matkor>
print_int m.member; (* syntax error *)
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<sam_>
as far as i remember (i don't really use classes / objects), you can't access data members straight, so you'd need to make accessor functions.. and secondly, object members are references with #, not with ".".. so you'd want "m#member", instead of "m.member" (note: m#member won't work in this case either)
<matkor>
sam_: Thanks :)
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<matkor>
Is there any C++ printf equvalent in ocaml :) ? I'm bored with print_that that; print_this this; :) ?
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<sam_>
Format.printf
<sam_>
if you mix that with the print_ stuff, you might get some unexpected output, as they use different buffers (c standard buffers vs. caml buffers). so if you mix them, you might need to use Format.flush / Pervasives.flush
<sam_>
oh, and printf isn't type safe, so if you'll get core dumps, you might want to look into what you give printf as params
<matkor>
Thanks again sam :) .
<sam_>
hmm, actually, i think i was wrong about Format.printf not being type safe. Looks like they've done some type hack just for it in the language
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<matkor>
yeah, enough for tonight :) thanks for help, sam, and good bye :)