[racket] Basic inquiry

Dear Matthias,

This is what I needed. I did not understand how to use string-ith.  Now I
do.  Thank you very much.

Laurent also sent me links to some beginner's intro videos on You Tube.

I am amazed and eternally grateful that people of your calibre would take
the time and trouble to help a tyro like me who must seem like an annoying
gnat to you.

Thank you guys.

Saad
PS I will probably trouble you again.  Will try to keep it to minimum.

On Sat, May 12, 2012 at 4:40 PM, Matthias Felleisen <matthias at ccs.neu.edu>wrote:

>
> On May 12, 2012, at 8:35 AM, saad bashir wrote:
>
> Dear Matthias,
>
> Thank you for replying to me.  I am sure this is laughably basic for you.
>
>
> It is basic for me, but there's nothing laughable.
>
>
> I got what you wrote.  I know string-ith extracts the letter.  My question
> is how to use it. I have tried various ways of writing both in the def and
> interaction sections but have not worked out.  Even consulting the Helpdesk
> has not helped as it does not tell me how to use the fucntion.
>
> Sorry if I am being very thick. I really want to do it right.
>
>
>
> If you have a DrRacket in front of you, does it say
>
>   "Welcome to DrRacket, version 5.2.1"
>   Language: Beginning Student.
>
> in the Interactions WIndow? If not, you need to switch languages with the
> Language menu.
>
> Once you have switched languages, click run. Then try these interactions:
>
> > (string-ith "hello world" 0)
> "h"
> > (string-ith "hello world" 1)
> "e"
> > (string-ith "hello world" 2)
> "l"
> > (string-ith "hello world" 3)
> "l"
> >
>
> Please let me know which step went wrong previously. -- Matthias
>
>
>
>
>
> Saad
>
> On Fri, May 11, 2012 at 11:47 PM, Matthias Felleisen <matthias at ccs.neu.edu
> > wrote:
>
>>
>> The beginning of section 2.1.3 looks like this:
>>
>>
>> > All other operations concerning strings consume or produce data other
>> than strings. Here are some examples:
>> >       • string-length consumes a string and produces a (natural) number;
>> >
>> >       • string-ith consumes a string s and extracts the one-character
>> substring located at the ith position (counting from 0); and
>> >
>> >       • number->string consumes a number and produces a string.
>> >
>> > Also look up substring and find out what it does.
>>
>> Which function do you think extracts a "letter" from a string? [[You can
>> follow the links for the function names. Perhaps it is easier to read the
>> docs.]]
>>
>> -- Matthias
>>
>>
>>
>>
>> On May 11, 2012, at 4:22 PM, saad bashir wrote:
>>
>> > I am back again.  I had a basic inquiry and your help got me started.
>> >
>> > My problem is as follows:
>> >
>> > I have just started to work through 2Htdp (i.e. the second edition)
>> that you had guided me to. Having gone through the prologue I am now on the
>> second chapter, "Fixed-size data."  But have got stuck almost at the start.
>>  I have successfully done the first two exercises but have hit a road block
>> on exercise 3 (section 2.1.3 "Mixing it up").  I do not know what
>> instruction to use to insert or extract a letter from the ith position.  I
>> think I am doing something wrong when trying to look up things in Helpdesk.
>> Please help.
>> >
>> > Saad
>> >
>> > On Fri, Apr 27, 2012 at 8:32 PM, Danny Yoo <dyoo at cs.wpi.edu> wrote:
>> > On Fri, Apr 27, 2012 at 11:27 AM, saad bashir <bashir.saad at gmail.com>
>> wrote:
>> > > Your help was great.  Things are working now.  And a great thank you
>> for
>> > > leading me to the 2d edition of How to Design Programs.  I had not
>> known
>> > > about it.
>> >
>> >
>> > Glad to hear that it's working for you now!  Please feel free to
>> > continue to ask questions on the mailing list; we'll be happy to help.
>> >
>> > ____________________
>> >  Racket Users list:
>> >  http://lists.racket-lang.org/users
>>
>>
>
>
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