I am defining like this in eiffel to swap the value. We cannot use the way we define in c++.

 swap(x,y):INTEGER
         do
            x;y := y;x
       end

How to define functions in Eiffel? I want to define heap sort but it is showing some error can someone help me clear my doubt about function.

 heapsort(array,N):INTEGER  -- heap_sort
            do
                heap_size : INTEGER
                heap_size := N

                build(array,N)

                from i := N until i >=2 loop

                    swap(array(1), array(i))
                    heap_size := heap_size-1
                    heapify(array,1,heap_size-1)

                end
            end

Is writing one rescue clause at the end of a program to end the program in Eiffel enough to handle exceptions such as pre, postconditions or invariant violations in any of the routines written in the program? Or should I write rescue clause for every function having pre and postconditions to handle exceptions?

I have read Eiffel documentation on error handling but I couldn't figure out.

Given a file input.txt, which consists of a number of elements in arrays and elements in the arrays, I should read the data and copy it to arrays in Eiffel. For example, for

3 
3 4 5
2 3 1

I should get len = 3, a1 = {3,4,5}, a2 = {2,3,1}.

I have tried the following but it was not successful

take_input
        -- Read user's input.
    local
        input: PLAIN_TEXT_FILE
        output: PLAIN_TEXT_FILE
        itr: INTEGER
    do
        create input.make_open_read ("input.txt")
        input.read_integer
        len := input.last_integer
        create output.make_open_write ("output.txt")
        create num.make_filled (0, 1, len)
        create rem.make_filled (0, 1, len)
        from
            input.start
            input.read_integer
            itr := 0
        until
            input.off
        loop
            itr := itr + 1
            if itr <= len then
                num [itr] := input.last_integer
                input.read_integer
            else
                rem [itr - len] := input.last_integer
                input.read_integer
            end
        end
        input.close
    end

Here Is there any way I can continously read the inputs rather than again starting from the Begginning of the file?

How can a mail be sent in eiffel with kernel library? which class to use?

Which library of the kernel should I use to sort a collection in eiffel?

where can I find an example of sort? are the tipical bubble sort, etc available?

Any sorter with agent would be very useful too to avoid having to do it with a comparable which is not implemented for example with PATH class

As I'd like to know if some object is into a LINKED_SET to prune it in my context, I'm unable to compare it as an object instead of its reference.

changeable_comparison_criterion: BOOLEAN
        -- May `object_comparison' be changed?
        -- (Answer: only if set empty; otherwise insertions might
        -- introduce duplicates, destroying the set property.)
    do
        Result := is_empty
    ensure then
        only_on_empty: Result = is_empty
    end

Into the SET class (as above) it seems that its not possible to change a set to compare_objects. So my questions are:

1. What is the semantic of not being able to compare objects into a SET
2. If my choice of LINKED_SET is wrong by misunderstanding of its semantic, how should I do for having a unique items collection based on object comparison and then being able to prune an item again based on object comparison again

I really don't understand as it seems to me the basics of type conformance. I have a Creation instruction lists explicit creation type which does not conform to type of target on create {JANITZA_DEVICE} l_device.make_from_file_path (a_file_path) with eiffel studio 19.5 enterprise.

SMA_INVERTER_MANAGER_CSV

class
    SMA_INVERTER_MANAGER_CSV

inherit
    SUNSPEC_DEVICE_CSV[SMA_INVERTER_MANAGER_DEVICE]

create
    make

SUNSPEC_DEVICE_CSV

deferred class
    SUNSPEC_DEVICE_CSV[G -> SUNSPEC_DEVICE create make_from_file_path end]

inherit
    CONSUMPTION_SECTOR_CSV[G]
        redefine
            process_file,
            set_header_csv
        end

feature --

    process_file (a_file_path: PATH)
        require else
            attached a_file_path.entry
            attached consumption_sector
        local
            l_device: like devices.item
        do
            check
                attached_consumption_sector: attached consumption_sector
            then
                if is_valid_file_path (a_file_path) then
                    if attached a_file_path.utf_8_name.has_substring ("janitza_UMG604") then
                        create {JANITZA_DEVICE} l_device.make_from_file_path (a_file_path) -- The compiler doesn't agree!
                    else
                        create l_device.make_from_file_path (a_file_path)
                    end
                    l_device.load_measuring_point (create_measuring_points, measuring_point_db_service, consumption_sector)
                    devices.extend (l_device)
                    Precursor (a_file_path) -- load measure_units from csv_row
                    devices.wipe_out
                end
            end
        ensure then
            devices.is_empty
        end

CONSUMPTION_SECTOR_CSV[G]

deferred class
    CONSUMPTION_SECTOR_CSV[G -> MEASURING_POINT_DEVICE]

feature -- Access

    devices: LINKED_SET[G]

SUNSPEC_DEVICE

class
    SUNSPEC_DEVICE

inherit
    MEASURING_POINT_DEVICE
        redefine
            default_create,
            set_measuring_point,
            out
        select
            serial
        end

    MODBUS_DEVICE
        rename
            serial as modbus_serial,
            set_serial as set_modbus_serial
        undefine
            make
        redefine
            default_create,
            make_from_file_path,
            name_from_file_path,
            out
        select
            set_modbus_serial
        end

create
    make_from_file_path

JANITZA_DEVICE

class
    JANITZA_DEVICE

inherit
    SUNSPEC_DEVICE
        redefine
            set_measure_units,
            name_from_file_path
        end

create
    make_from_file_path

Repeatedly inheriting from 2 classes having the same parent, I fall into the classic case of inheriting 2 times of the same attribute. I'd like to merge the 2 attributes into one and tried to do it with an undefine, but it gets me a compile error. The other solution I see is renaming the attribute from one of both parents, but as I understand each instance of my D class would have an useless attribute which is not what I want...

Error: Undefine subclause lists name of frozen feature or attribute or C external. What to do: unless you can change the status of the feature in the parent, remove its name from Undefine subclause since it cannot be undefined.

How to merge 2 attributes from repeatedly inherited classes

class A
    serial: STRING

end -- class A

class B

inherit
    A

end -- class B


class C

inherit
    A

end -- class C


class D

inherit
    B
        undefine 
            serial -- error seems to appear here in that case
        end
    C

end -- class D

How to specify when giving a generic parameter that it should implement some specific creation method? as LIST[G -> create make end] doesn't work :-(

In my particular case, * SMA_INVERTER_MANAGER_CSV has inherited from CONSUMPTION_SECTOR_MODBUS_DEVICE_CSVa list of devices as devices: LINKED_SET[G] as G -> MEASURING_POINT_MODBUS_DEVICE create make_from_file_path end.

I'd like the SMA_INVERTER_MANAGER_CSV class to be able into devices: LINKED_SET[G] to be able to have either JANITZA_DEVICE, SUNSPEC_DEVICE, ABB_DEVICE, etc. Giving the generic parameter as MEASURING_POINT_MODBUS_DEVICE seems to come out of a sense, but how do I specify that I'd like the creation method to be make_from_file_path

Hope the description is sufficient to understand, refactoring I think this question is linked -> explicit creation type not conforming to type of target

The only workaround for the moment I found working for the moment is

class
    SMA_INVERTER_MANAGER_CSV

inherit
    CONSUMPTION_SECTOR_MODBUS_DEVICE_CSV[SUNSPEC_DEVICE]

create
    make


end

but I'd like it to be

class
    SMA_INVERTER_MANAGER_CSV

inherit
    CONSUMPTION_SECTOR_MODBUS_DEVICE_CSV[MEASURING_POINT_MODBUS_DEVICE]

create
    make


end

which would generate a conformance problem because MEASURING_POINT_MODBUS_DEVICE generic parameter doesn't specify make_from_file_path as creation procedure as its deferred

I have an assignment that requires me to create an empty linked list key: LINKED_LIST [KEY], another linked list data_items_1: LINKED_LIST [DATA1] and a hash table data_items_2: HASH_TABLE [DATA2, KEY] in the constructor. The post condition that my professor put was

object_equality_for_keys: keys.object_comparison
object_equality_for_data_items_1: data_items_1.object_comparison
object_equality_for_data_items_2: data_items_2.object_comparison

When I run the program I get a contract violation. In the debugger it's always pointing to this line of code and I'm not sure why. What is the purpose of this post condition and how do I not violate this contract?

I have a method that shifts all the items, in an array, to the left by one position. In my post condition I need to ensure that my items have shifted to the left by one. I have already compared the first element of the old array to the last element of the new array. How do i across loop through the old array from 2 until count, loop through the new array from 1 until count-1 and compare them? This is my implementation so far.

        items_shifted:
                    old array.deep_twin[1] ~ array[array.count]
                        and
                    across 2 |..| (old array.deep_twin.count) as i_twin all
                        across 1 |..| (array.count-1) as i_orig  all
                            i_twin.item ~ i_orig.item
                            end
                        end



    end

I expected the result to be true but instead I get a contract violation pointing to this post condition. I have tested the method out manually by printing out the array before and after the method and I get the expected result.

As far as I understood the check with then is mandatory.

So what is the semantic of having to declare a local to avoid compiling error (object could be void)?

detachable dog: DOG

take_a_walk
    do
        check
            attached_dog: attached dog as l_dog
        then
            leash (l_dog) -- why not just leash (dog)?
            walk
        end
    end     

I'd like to create a class with both an instance_free (ensure class) feature and a deferred one.

why is that I can't call an instance_free feature in a deferred class but only on a descendant?

Don't understand the logic of that... is there for compiling reasons? or any sense I don't see? Where am I wrong with my logic?

Didn't find the answer on this doc, is the rescue clause called when redefining a feature?

Class A

class A

feature -- 

    process
        do
            do_stuff
        rescue
            on_fail
        end
end -- class

Class B

class B

inherit
    A
        redefine
            process
        end

feature -- 

    process
        do
            do_other_stuff -- do I have to call the rescue too?
        end
end -- class

I'm looking for a way to call Precursor on another feature. The context is that I redefine a routine calling another heir's feature that calls mine, and I'd like to call it explicitly. Is there a way to do something such as in java Precursor.feature_a.

If not, the only alternative I find is to write a feature_a_implementation and call it from redefined feature. Is there a particular reason not to have this mechanism? The consequences of doing that would be to define 2 times the contract of feature_a into feature_a and feature_a_implementation

Is there a way to get the project name and target at execution time or is it not stored into executable?

As mentioned on this question, there is no way to define a constant which I can redefine into a descendant.

In many of my cases, I'd like to have a constant which I can redefine. The alternatives I see to avoid a creation on each consultation which doesn't make sense would be

That's not doable

class A

feature -- Access

    Default_value: STRING = "some A value"

end -- Class


class B

inherit
    B
        redefine
            Default_value
        end

feature -- Access

    Default_value: STRING = "some B value"

end -- Class

Alternative with once instance_free

class A

feature -- Access

    Default_value: STRING
        once
            Result := "some A value"
        ensure
            instance_free: class
        end

end -- Class


class B

inherit
    B
        redefine
            Default_value
        end

feature -- Access

    Default_value: STRING
        once
            Result := "some B value"
        ensure
            instance_free: class
        end

end -- Class

As far as I understand, the once wouldn't be created with B value as the A class value would be taken

Alternative with attribute

class A

feature -- Access

    Default_value: STRING
        attribute
            Result := "some A value"
        ensure
            instance_free: class
        end

end -- Class


class B

inherit
    B
        redefine
            Default_value
        end

feature -- Access

    Default_value: STRING
        attribute
            Result := "some B value"
        ensure
            instance_free: class
        end

end -- Class

Would it be the only and good practice to do it?

I'd like to do grouping of regular expressions with eiffel. How do I do something like

l_reg.compile ("^([0-9]{3}) (rabbit[0-9]).*")
l_groups := l_reg.groups ("123 rabbit1")
my_first_rabbit := l_groups.at (2)

Didn't find any example on groups, LX_DFA_REGULAR_EXPRESSION class and other googlings

Id like to uncompress a file with bzip2 myFile.bz2 which class do I have to use for that?

I tried to find it into base kernel documentation which made the most sense for me and didn't find it

How do I concatenate a percent % string to a string?

as either do not work

s := "%%" + s + "%" 

I know its a special character but don't afford it neither do I find the doc...

UPDATE

The answer was one of my attempts, but it could stay an issue of the compiler/editor. After putting the example into the same feature, compiling, and replacing the old code the compiler did not complain anymore, but still stays as syntax coloration strange

As per this documentation, I'm trying to constrain a Generic parameter to 2 classes and need a default_create creation procedure call in my implementation.

I'm getting a Syntax error from compiler on the select clause. Why is that so?

I thought first that calling default_create will call the G one which could be a merge/renaming/etc. but seems that on that level I have to call either one of both or both renamed which makes sense for me. But why does this syntax fail?

The context and my code is following:

deferred class
    IDENTIFIABLE_CASH[G -> {IDENTIFIABLE[ANY],
                            DB_ENTITY select default_create end} create default_create end]

inherit
    DB_SERVICE_CASH[G]


feature -- Access

    cash_from_identifier (an_identifier: like {IDENTIFIABLE_DB_ENTITY[ANY]}.identifier): G
            -- Returns firt entity found like given an_identifier (like operator is used)
        local
            l_qry: COMPOSED_SQL_QUERY
        do
            across
                cash is l_item
            loop
                if l_item.identifier.is_equal(an_identifier) then
                    Result := l_item
                end
            end
            if not attached Result then
                create l_qry.make (item_prototype)
                l_qry.add_constraint (create {FIELD_CONSTRAINT}.make (Void, identifier_db_column_name, {CONSTRAINT}.Like_operator, an_identifier))
                load_entities (l_qry)
                if items.count > 0 then
                    Result := items.first
                else
                    create Result
                    check
                        item_not_found: False
                    end
                end

                cash.extend (Result)
            end
        end

Am looking for typical

feature {NONE} -- Initialization (semantic)
feature -- Status Settings (semantic)
.....

Where can I find that list with semantic?

Didn't find it into ECMA

Got a Catcall trying to compare 2 types, how could I do that avoiding passing through another not dedicated method (like to string, class_id or stuff like that)?

SIT_UTIL

    class_name_lowercase (a_string: STRING): STRING
            -- a copy lowercased and pruned from preceding '!'
        do
            Result := a_string
            if Result.index_of('!', 1) = 1 then
                Result := Result.substring (2, Result.count)
                Result.to_lower
            else
                Result := Result.as_lower
            end
        ensure
            instance_free: class
        end

CLIENT_CLASS

    relationship_from_secondary_type_equal (a_type: like relationships.item.secondary_type): detachable like relationships.item
            -- Returns first instance of found relationship secondary type which equals given one
        do
            across
                relationships as l_rel
            until
                Result /= Void
            loop
--              if attached (a_type / l_rel.item.secondary_type) then -- Don't want conformance but equality

--              if attached (a_type.is_equal (l_rel.item.secondary_type)) then -- tried but as is_equal needs a like Current => Catcall
--              if attached (a_type.equal (a_type, l_rel.item.secondary_type)) then -- Catcall because b signature is like a
                if {SIT_UTIL}.class_name_lowercase (a_type).is_equal({SIT_UTIL}.class_name_lowercase (l_rel.item.secondary_type)) then
                    Result := l_rel.item
                end
            end
            check
                not_found_relationship: Result /= Void
            end
        end

I'm trying to do something as

work (a_father: FATHER)
    do
        if a_father.conforms_to ({DEVELOPER}) then
           a_father.code
        else
           a_father.change_job ({DEVELOPER})
        end
    end

the compilation works, but in my implementation @runtime it doesn't pass. What did I mistype?

Is there a way (I'm sure there is out of runtime check...) to specify that a parameter or a variable in general conforms to multiple types? to avoid doing something such as

work (a_printer: PRINTER; a_scanner: SCANNER)
    do
      a_printer.print
      a_scanner.scan
        -- OR without second parameter
      if attached {SCANNER} a_printer as l_scanner then
         l_scanner.scan
      else
         throw RuntimeError
      end
    end

I attempted to install the Traffic library for the book "A Touch of Class" but was not able to compile the examples. EiffelStudio complained about a base2.ecf file. Error code: VD00

General configuration parsing error. What to do: fix the configuration file.

Could not open file: \base2.ecf $EIFFELBASE2\base2.ecf

base2.ecf is found in where Windows installed Eiffel: C:\Program Files\Eiffel Software\EiffelStudio 18.11 GPL\unstable\library\base2.ecf The offending line of code seems to be this in the Traffic configuration files:

I have attempted to change this configuration file pointing directly to where the file is, using the actual path, to no avail.

I'm really stuck in how to pass an argument to a second level of an Eiffel agent call. Hope my example is enough self explaining:

main_call
    do
        b (agent d(?, ?))
    end

b (a_proc: PROCEDURE[STRING])
    local
        l_something_else: INTEGER
    do
        l_something_else := 1
--        z("a_line", a_proc(l_something_else)) -- How can I pass at this stade l_something_else to the d procedure!!!
    end

d (line: STRING; something_else: INTEGER)
    do
--        do_some_stuff_with_line (line, something_else)
        do_nothing
    end

z (a_line: STRING; a_proc: PROCEDURE[STRING])
    do
        a_proc.call([a_line])
    end

I would have liked to be able to do something like

z("a_line", a_proc(?, something_else))

But its not possible, as I try with the agent keyword, the a_proc argument is not recognized!

So what would be the syntax? I even tried to add an argument to a_proc with a_proc.set_operands but am lost with the OPEN_ARGS class

Implementation case

If you need a goal... just imagine I'd like to have 2 different implementations of the d function, and in my case its using UT_CSV_HANDLER that I'd like to have 2 different functions for each line of a CVS

The following code gives a Non-compatible actual argument in feature call

Feature: import_from_csv_impl
Called feature: import_from_csv_impl (a_rest_request: REST_REQUEST; a_procedure: PROCEDURE [DS_ARRAYED_LIST [STRING_8], INTEGER_64, STRING_8]): [detachable like items] detachable SIT_LINKED_LIST [MEASURING_POINT] from MEASURING_POI...
Argument name: ia_name
Argument position: 2
Formal argument type: STRING_8
Actual argument type: INTEGER_64
Line: 258
                ia_procedure.call (ia_measuring_point_id, ia_name)
->            end (?, l_measuring_point_id, l_s)
            l_csv_handler.read_file (l_is, l_partially_closed)

The complete example:

-- Main call
import_from_abb_csv (a_rest_request: REST_REQUEST): detachable like items 
    do
        Result := import_from_csv_impl (a_rest_request, agent impl_for_each_csv_line_import_from_abb_csv)
    end

-- Second call
import_from_csv_impl (a_rest_request: REST_REQUEST; a_procedure: PROCEDURE[DS_ARRAYED_LIST [STRING_8], INTEGER_64, STRING]): detachable like items
    local
        l_csv_handler: UT_CSV_HANDLER
        l_is: KL_STRING_INPUT_STREAM
        l_measuring_point_id: INTEGER_64
        l_s: STRING
        l_partially_closed: PROCEDURE[DS_ARRAYED_LIST[STRING]]
    do
        l_s := "whatever"
        l_measuring_point_id := 12
        create l_csv_handler.make_with_separator (',')

        l_partially_closed := agent (i_al: DS_ARRAYED_LIST[STRING]; ia_measuring_point_id: INTEGER_64; ia_name: STRING; ia_procedure: PROCEDURE[INTEGER_64, STRING])
            do
                ia_procedure.call (ia_measuring_point_id, ia_name)
            end (?, l_measuring_point_id, l_s)

        l_csv_handler.read_file (l_is, l_partially_closed)

    end

-- end call
impl_for_each_csv_line_import_from_abb_csv (a_csv_line: DS_ARRAYED_LIST [STRING_8]; a_measuring_point_id: INTEGER_64; l_cu_name: STRING)
    do
        -- do_my_business
    end


-- for information signature of read_file is:
--     read_file (a_file: KI_TEXT_INPUT_STREAM; a_action: PROCEDURE [DS_ARRAYED_LIST [STRING]])

General

I don't understand why there are like 2 generating_type kinds, the one with exclamation point, and the other not.

My case

I have a function returning a DB_SERVICE[G] from a given instance from a collection of db_services so that from another service I can retrieve it and call it. When I pass an instance generating_type to that function, the conforms_to returns True, as when I give ({ENUMERATE}).generating_type it doesn't.

Why is that so?

-- Humanly unreadable
if attached {ENUMERATE_DB_SERVICE} {SIT_ENVIRONMENT}.app_instance.db_service_from_entity_type (item_prototype.charge_unit_relationship.secondary_prototype.an_index_relationship.secondary_prototype.generating_type) as l_enum_dbs then

-- Humanly readable but not working
if attached {ENUMERATE_DB_SERVICE} {SIT_ENVIRONMENT}.app_instance.db_service_from_entity_type (({ENUMERATE}).generating_type) as l_enum_dbs then

My function

db_service_from_entity_type (an_entity_type: TYPE[detachable DB_ENTITY]): detachable like db_services.item
    do
        across
            db_services as l_dbs
        until
            Result /= Void
        loop
            if l_dbs.item.item_prototype.generating_type.conforms_to (an_entity_type) then
                Result := l_dbs.item
            end
        end
    ensure
        service_found: attached Result
    end

Edit (20190405-11:26 UTC)

As the screenshot shows, giving {ENUMERATE} instead of ({ENUMERATE}).generating_type doesn't work either

Seems I'm wrong creating a datetime from string using this method, any idea why? The precondition violates on date_time_valid: date_time_valid (s, code)

create l_date_time.make_from_string ("2019-03-28T15:28:02Z", "yyyy-mm-ddThh:mi:ssZ")