Re: Reading in floats from strings???

Thanks guys.  These were excellent suggestions, and none of them were that
difficult to implement.  Thanks again!  Sorry about that other message.  I
didn't realize that the group doesn't allow messages with attachments.  ( I
guess that's for security reasons, but maybe I'm wrong. )

Just curious, but are there any colleges, universities, online schools,
etc, that offer a program of study in Ocaml?  Most of the CS programs in my
city teach either C, C++ or Java.  I don't know of any school around here
that offers training in a functional programming language.


On Wed, Jan 27, 2016 at 12:28 PM, Gabriel Scherer [email protected]
[ocaml_beginners] <[email protected]> wrote:

>
>
> My quick&dirty way to parse numeric values in string format is Scanf,
> using formats of the kind " %d" (for integers) and " %f" (for floats), with
> the space having the meaning of "ignore any space before".
>
> It is easier to do on the standard input directly:
>
>   let read_next_float () = Scanf.scanf " %f" (fun x -> x)
>
>   let () =
>     let x = read_next_float () in
>     let y = read_next_float () in
>     print_float (x +. y)
>
> if your input comes from a string, you have to convert it into a scanning
> buffer first:
>   http://caml.inria.fr/pub/docs/manual-ocaml/libref/Scanf.html
>   http://caml.inria.fr/pub/docs/manual-ocaml/libref/Scanf.Scanning.html
>
>   let read_next_float input = Scanf.bscanf input " %f" (fun x -> x)
>
>   let sum_of_string str =
>     let input = Scanf.Scanning.from_string str in
>     let x = read_next_float input in
>     let y = read_next_float input in
>     (x +. y)
>
> Please be aware, however, that Scanf is best used for programs where you
> control the input. It does not perform much input validation, and if you
> want to provide a convenient user interface to your user and be robust to
> formatting errors, you should use a more robust parsing strategy. I have
> never personally been in the situation where regexp parsing felt like the
> right compromise between expressivity and convenience, I tend to move to
> full lexer+parser stacks directly (which are easy to use in OCaml, see
> [sedlex] + [menhir]), but that's a question of habits I guess.
>
>  sedlex: https://github.com/alainfrisch/sedlex
>  menhir: http://gallium.inria.fr/~fpottier/menhir/
>  compiling a project using both:
> http://stackoverflow.com/questions/30853159/using-menhir-with-sedlex
>
> On Wed, Jan 27, 2016 at 10:29 AM, Douglas Lewit [email protected]
> [ocaml_beginners] <[email protected]> wrote:
>
>>
>>
>> Hi everyone,
>>
>> I am new to this list, so I thought I would introduce myself.  Also, I
>> have a question about how to read in data of the form "11.3  12.9".
>> Obviously a string, but I need to extract the floats contained in the
>> string.  I know how to do that in Java and also in Python, but for me Ocaml
>> is still pretty much a foreign language.  I appreciate any guidance you can
>> offer.
>>
>> Anyhow, I've got a master's in math from a small state university in
>> Chicago, Illinois.  I'm currently working on a second master's in CS at the
>> same university.  My work experience is mostly in teaching, although I've
>> also done some retail management.  I used to be a high school math teacher
>> ( mostly Catholic high schools, but also have some experience in the public
>> school system ) and currently I teach part-time at Oakton Community College
>> ( near Chicago ).  I'm interested in leaving education within the next
>> couple of years to find a new career in the software industry.  My age
>> could be a factor that works to my disadvantage, since most of the people
>> that I personally know in various startup companies are quite young.  (
>> I've been to some Python and Ruby meetups in the Chicago area, and I get
>> the distinct impression that the vast majority of attendees are under the
>> age of 35. )
>>
>> Ocaml is appealing to me for a couple of reasons.  Well first off, how
>> can I resist a book that has a picture of a lovable camel on its front
>> cover!!!   ;-)   But on a more serious note, I like Ocaml because it really
>> forces the programmer to get over his fear or hatred of recursion.  I think
>> recursion is sort of optional in many other languages, and in fact some
>> programmers really hate it because it does require a different way of
>> thinking about problems.  But in Ocaml recursion is not optional.  So for
>> me it's a really good exercise in thinking recursively about various
>> problems.  Although sometimes I think Ocaml goes a little too far with its
>> emphasis on recursion.  I mean.... there are times when a nice little for
>> loop or while loop would do the job with far greater simplicity!
>>
>> From the reading I have done on the web it appears that Ocaml is a big
>> hit with Jane Street, a very large financial trading company with offices
>> in NYC, London and Hong Kong.  Outside of Jane Street, where is Ocaml used?
>>
>> Take care and thanks for reading my intro message.
>>
>> Best,
>>
>> Douglas Lewit
>>
>> P.S.  Is there any connection between Ocaml and Wolfram Mathematica?
>> Both begin and end comments with (* and *), respectively, and both
>> emphasize the functional approach to programming.  I'm a big fan of
>> Mathematica, and often incorporate it into math classes that I teach.  I'm
>> just wondering if there's a connection between the two software projects.
>> Thanks.
>>
>>
>>
>>
> 
>