String to Integer

String to Integer

[Charles Hill]

I have a string in which an integer is stored.  I'd like to hear
from someone who might know a convenient way to convert this to
an actual integer.  I'm wondering if there is a function built
into one of the Ada packages to do this, but I haven't found one
yet.

I would appreciate any advice anyone has.

Thanks,

-Brian Hill
--
Charles Brian Hill			    Florida State University
hill@cs.fsu.edu				 Computer Science Department

Re: String to Integer

[John Herro]

hill@cs.fsu.edu (Charles Hill) writes:
> I have a string in which an integer is stored.
> I'd like to ... convert this to an actual integer.
> I'm wondering if there is a function built into
> one of the Ada packages to do this...

Not into an Ada *package*, but built into the language itself.
If S is the string and I is an Integer variable, you can write

I := Integer'Value(S);

The 'Value is called an attribute.  The 'Image attribute goes the
other way, so you could also write

S := Integer'Image(I);

'Image and 'Value work with many types, not just Integer, but
they always convert to and from strings.  For more information,
you can download the Ada Tutor program from the Web or FTP
sites below my signature.  I hope this helps.

- John Herro
Software Innovations Technology
http://members.aol.com/AdaTutor
ftp://members.aol.com/AdaTutor

Re: String to Integer

[Robert Dewar]

Charles says

<<I have a string in which an integer is stored.  I'd like to hear
from someone who might know a convenient way to convert this to
an actual integer.  I'm wondering if there is a function built
into one of the Ada packages to do this, but I haven't found one
yet.
>

A good piece of advice for beginning Ada programmers is to read through
the list of attributes in the back of the RM. You won't understand them
all, but you will dig up a number of useful things that wil otherwise
escape your attention (e.g. min, max, and in this particular case,
value, which will do the trick for you). You can of course also use
Text_IO's read from string.

Re: String to Integer

[Martin C. Carlisle]

In article <5qglt7$cba$1@news.fsu.edu>, Charles Hill <hill@cs.fsu.edu> wrote:
>I have a string in which an integer is stored.  I'd like to hear
>from someone who might know a convenient way to convert this to
>an actual integer.  I'm wondering if there is a function built
>into one of the Ada packages to do this, but I haven't found one
>yet.

Usually you can find any similar thing you might need in Ada.Text_IO

In your case (e.g.):

Ada.Integer_Text_IO.Get(From => My_String, Item => Integer_Value, Last =>
  Last_Location_Read_From_String);

There is also a shorter method using attributes:

Integer_Value := Integer'Value(My_String);

--Martin

-- 
Martin C. Carlisle, Computer Science, US Air Force Academy
mcc@cs.usafa.af.mil, http://www.usafa.af.mil/dfcs/bios/carlisle.html
DISCLAIMER:  This content in no way reflects the opinions, standard or 
policy of the US Air Force Academy or the United States Government.

Re: String to Integer

[Samuel Mize]

Charles Hill wrote:
> 
> I have a string in which an integer is stored.  I'd like to hear
> from someone who might know a convenient way to convert this to
> an actual integer.  I'm wondering if there is a function built
> into one of the Ada packages to do this, but I haven't found one
> yet.
> 
> I would appreciate any advice anyone has.

Do you mean that the string contains the characters that
represent the number, or that the string storage is also
used as binary storage for an integer?

In the first case (e.g. "301") you can use integer'image and
integer'value to translate between the string and the integer
value.  If your string is a buffer that may have garbage after
the end of the number (e.g., a null-terminated varying-length
string in a fixed-length buffer), it may be simpler to use
Ada.Text_Io.Integer_Io.Get from string, since it stops at the
first non-numeric character (while Integer'Value would try to
translate the entire string, and fail if there is anything in
it but the integer and blanks).

If you have a binary representation of an integer in your
string, you should use unchecked_conversion.

Samuel Mize

Re: Embedding Text Data in Source (Was Re: String to Integer)

[Samuel T. Harris]

John M. Mills wrote:
> 
> I have a question which diverges slightly from the original topic, but is
> somewhat related.  Please redirect me to "Read The Fine Manual" if that
> is appropriate, but be specific if you can.
> 
> I now provide object parameters for a program in the form of a number of small
> files whose names are passed to the <ObjectType1>.Create(ParamFileName1, ...)
> procedures for each of the objects in my model.  This works fine.  I would
> also like to have a set of default parameters compiled into the code.  Hard-
> coding this would be simple, but I want instead to include as the default
> a specified file from my source tree, verbatim, then use the same parsing
> routines to process either the file image embedded in the code or one read
> under a file name, as transparently as possible using approaches similar to
> the earlier suggestions in this thread: String'Value( ParamStr ) ... etc.
> 
> The present form of my parameter files is similar to this:
> 
> ! comment description
> VersionIDString    ! string to match for error checking
> ! comment lines as desired
> RealValueString    ! parameter value
> ! descriptive comment(s)
> IntegerValueString ! parameter value
> EnumValueString    ! and so forth, with '*ValueString's in fixed order
> ...
> 
> There is no guarantee that a line will have a specific length, but the
> sequence and grouping of parameters by [non-comment] line is well-defined.
> 
> THE QUESTION:
> How can I embed those files' contents in my code automatically at compilation
> so they can be parsed as strings?
> 
> Hope I managed to explain that .. &:^P   I am using GNAT on a variety of
> UNIX platforms.
> 
> Thanks -- john mills --
> 
> --
> John M. Mills, Senior Research Engineer   --   john.m.mills@gtri.gatech.edu
>    Georgia Tech Research Institute, Georgia Tech, Atlanta, GA 30332-0834
>         Phone contacts: 404.894.0151 (voice), 404.894.6258 (FAX)
>  "The 'Quick and Dirty' approach can generally be relied on to be dirty."-RlF

My personal coding standard has long included producing an image and
value
function for any interesting aggregate (record or array) type and these
functions work with strings which appear as Ada aggregates. This way
I can initialize such objects with aggregates in the code, or copy
the aggregate source itself to a data file which I read at runtime.
I find the interoperability of the format to be a great time saver.

I use functions parse and format when I need a syntax which differs
from Ada aggregate syntax and I also sometimes provide a function debug
which produces a string with any extra intrernal debugging info I might
wish to include.

When using image/value, I can use the original source code aggregates
for my data file, and vice versa. No problem there. What is in a
particular
data file just becomes the source for an assignment statement. Cut and
Paste.

When using parse/format (as John would need since his syntax differs
from Ada aggregates) I need filtering utilities to convert the strings.
Since the syntax differs, I cannot use the data file in a direct
assignment
statement. I have to state the text of the data file in a string
and parse that string. The filtering involved is not very complicated.

1. Replace existing double quotes (") with two double quotes ("").
2. Prefix each line with a double quote (").
3. Suffix each line with a double quote (").
4. Add the following to each line except the last line ...

   & ascii.lf &

... if you wish to perserve the newlines implied in the file,
which is usually the case since the end of a line is often
an important delimiter.

5. You are done. The processed text can be inserted into your Ada code
as an source for a initialization of a string object (or constant string
object if you are using Ada83). Note that such a string should be hidden
inside a initialization procedure and not made global to a package.
If global, it will consume memory long after your program has no further
need for it. By staging it inside a procedure, it will (usually) be
placed on the stack as the procedure starts, and then clean away when
the procedure exits (and after you have processed it).

Filtering from such processed text in you Ada source back into a
data file involves performing the inverse steps in reverse order.

Processing John's example gives ...

init_string : constant string :=
"! comment description" & ascii.lf &
"VersionIDString    ! string to match for error checking" & ascii.lf &
"! comment lines as desired" & ascii.lf &
"RealValueString    ! parameter value" & ascii.lf &
"! descriptive comment(s)" & ascii.lf &
"IntegerValueString ! parameter value" & ascii.lf &
"EnumValueString    ! and so forth, with '*ValueString's in fixed order"
;

-- 
Samuel T. Harris, Senior Engineer
Hughes Training, Inc. - Houston Operations
2224 Bay Area Blvd. Houston, TX 77058-2099
"If you can make it, We can fake it!"

Embedding Text Data in Source (Was Re: String to Integer)

[John M. Mills]

I have a question which diverges slightly from the original topic, but is
somewhat related.  Please redirect me to "Read The Fine Manual" if that
is appropriate, but be specific if you can.

I now provide object parameters for a program in the form of a number of small
files whose names are passed to the <ObjectType1>.Create(ParamFileName1, ...)
procedures for each of the objects in my model.  This works fine.  I would
also like to have a set of default parameters compiled into the code.  Hard-
coding this would be simple, but I want instead to include as the default
a specified file from my source tree, verbatim, then use the same parsing
routines to process either the file image embedded in the code or one read
under a file name, as transparently as possible using approaches similar to
the earlier suggestions in this thread: String'Value( ParamStr ) ... etc.

The present form of my parameter files is similar to this:

! comment description
VersionIDString    ! string to match for error checking
! comment lines as desired
RealValueString    ! parameter value
! descriptive comment(s)
IntegerValueString ! parameter value
EnumValueString    ! and so forth, with '*ValueString's in fixed order
...

There is no guarantee that a line will have a specific length, but the
sequence and grouping of parameters by [non-comment] line is well-defined.

THE QUESTION:
How can I embed those files' contents in my code automatically at compilation
so they can be parsed as strings?

Hope I managed to explain that .. &:^P   I am using GNAT on a variety of
UNIX platforms.

Thanks -- john mills --

-- 
John M. Mills, Senior Research Engineer   --   john.m.mills@gtri.gatech.edu
   Georgia Tech Research Institute, Georgia Tech, Atlanta, GA 30332-0834
        Phone contacts: 404.894.0151 (voice), 404.894.6258 (FAX)
 "The 'Quick and Dirty' approach can generally be relied on to be dirty."-RlF

Re: String to Integer

[Michael F Brenner]

To convert strings to integers manually, examine the following
topics: finite state machines, loops, arrays, preconditions, +, *, and
assignment.

To convert automatically, examine the topics: image, value, pos, and
unchecked conversion, and text_io.

Re: String to Integer

[Samuel Mize]

Michael F Brenner wrote:
> 
> The best response to this was the list of topics to look up, given by
> Mike Brenner, not the actual solutions given by the others. Actual
> solutions should be available on the PAL, however, and should be
> referred to.
> 
> Mike Brenner


Gee, I wish I had the gall to denigrate the work of other people
and laud myself in the third person.

Define "best."  Do you really think a topic keyword is more
helpful than a brief description?  Or do you consider a less
helpful reply "better" somehow?  It's not like we were asked
for a whole homework assignment, just a pointer to a language
feature.

Any code in the PAL converting between strings and integers
would be a pretty suspect example to learn from, since it's
manually duplicating a built-in language feature (83 and 95).

By all means, though, keep directing new programmers to learn
about Ada by dredging through the megs of code at the PAL, if
you consider that the best way to communicate basic concepts.

Sam Mize

Re: Embedding Text Data in Source (Was Re: String to Integer)

[Matthew Heaney]

In article <5ql62v$8dp@acmey.gatech.edu>, jm59@prism.gatech.edu (John M.
Mills) wrote:


>I now provide object parameters for a program in the form of a number of small
>files whose names are passed to the <ObjectType1>.Create(ParamFileName1, ...)
>procedures for each of the objects in my model.  This works fine.  I would
>also like to have a set of default parameters compiled into the code.  Hard-
>coding this would be simple, but I want instead to include as the default
>a specified file from my source tree, verbatim, then use the same parsing
>routines to process either the file image embedded in the code or one read
>under a file name, as transparently as possible using approaches similar to
>the earlier suggestions in this thread: String'Value( ParamStr ) ... etc.

I'm not sure exactly what you're trying to do, but here's a suggestion. 
Can't you use a function call that returns a string as your default value? 
ie

function Default_Value return String;

procedure P (O : T := Default_Value);

and then the Default_Value function could parse a file, read an environment
variable, etc.  The function gets invoked at run-time, and only then if the
call of P doesn't have an explicit value as an argument.

Of course, if it's the same value every time it's invoked (it only changes
across program executions), then you can calculate that value once at
initialization, either via an explicit package initialization subprogram or
implicitly via package elaboration (be careful of the latter).

Is this in the ballpark of what you wish to do?

--------------------------------------------------------------------
Matthew Heaney
Software Development Consultant
<mailto:matthew_heaney@acm.org>
(818) 985-1271