Re: Euphoria vs. C and OOP
Bill Reed wrote:
>
>
> People have been saying that Euphoria should be more "C" like, or
> more "OOP" like. Euphoria has unique features that set it apart from
> C or OOP, and make it flexible, but in different ways.
>
> Instead of trying to make Euphoria fit into a C mold or OOP mold,
> take advantage of the unique features of Euphoria.
>
> sequences are structures, but not like C. They are just as flexible,
> perhaps even more so, since it is easier to add to or change what
> a sequence is.
>
> A sequence can be just a string, "ABC", or a structure:
> }}}
<eucode>
> a = {
> "ABC", -- string
> 123, -- integer or atom
> {"XYZ", 456} -- another sequence
> }
> </eucode>
{{{
> Referencing these members can be done with constants, like
>
> }}}
<eucode>
> constant NAME = 1, AMT = 2, DESC = 3,
> DNAME = 1, DAMT = 2
>
> a[NAME] ("ABC")
>
> or
> a[DESC] ( {"XYZ", 456} )
> a[DESC][DNAME] ("XYZ")
> a[DESC][DAMT] (456)
> </eucode>
{{{
>
> C has Public and Private functions. Euphoria can have them too,
> but in different ways.
>
> See the following include and program to see what I mean. I hope
> this can stimulate some discussion as to using Euphoria in a more
> structured way.
>
>
> ====================================================================
> == Member banking.e ==
> ====================================================================
> }}}
<eucode>
>
> --*----------------------------------------------------------------*
> --* banking.e bank account program *
> --* *
> --* Public *
> --* function BankProgram *
> --* *
> --* Private (or member functions) *
> --* function CreateAcct *
> --* function Withdrawal *
> --* function Deposit *
> --* procedure Balance *
> --* *
> --* example of account: *
> --* *
> --* a = {015505, "John Smith", 12000.15} *
> --* a[1] = acctno *
> --* a[2] = acctname *
> --* a[3] = balance *
> --*----------------------------------------------------------------*
>
> global constant
> acctno = 1,
> acctname = 2,
> balance = 3,
> blank_acct = {0, "", 0}
>
> function CreateAcct() -- Private function returns account
> sequence User_account
>
> User_account = blank_acct
> User_account[acctno] = 111000 -- assign next account #
> User_account[acctname] = prompt_string("Enter name : ")
>
> return User_account
>
> end function
>
> function Withdrawal(sequence account, atom amount) -- Private function
> account[balance] -= amount
>
> return account
>
> end function
>
> function Deposit(sequence account, atom amount) -- Private function
> account[balance] += amount
>
> return account
>
> end function
>
> procedure Balance(sequence account) -- Private procedure
> printf(1, "account : %d %s Balance : %.2f\n", {account[acctno],
> account[acctname],
> account[balance]})
>
> end procedure
>
> global function BankProgram(sequence parms)
> --*----------------------------------------------------------------*
> --* Public because it is global *
> --*----------------------------------------------------------------*
>
> sequence command, User_account, ret_account
> atom amount
>
> --*----------------------------------------------------------------*
> --* parms[1] = command *
> --* parms[2] = account (optional when creating new account) *
> --* parms[3] = optional amount *
> --* parms[4]... optional and expandable *
> --*----------------------------------------------------------------*
>
> command = parms[1]
>
> if equal(command, "new") then
> ret_account = CreateAcct()
> elsif equal(command, "Balance") then
> User_account = parms[2]
> Balance(User_account)
> ret_account = {}
> elsif equal(command, "Deposit") then
> User_account = parms[2]
> amount = parms[3]
> ret_account = Deposit(User_account, amount)
> elsif equal(command, "Withdrawal") then
> User_account = parms[2]
> amount = parms[3]
> ret_account = Withdrawal(User_account, amount)
> else
> puts(1, "Unknown command\n")
> return {}
> end if
>
> return ret_account
>
> end function
> </eucode>
{{{
>
> ====================================================================
> == end of Member banking.e ==
> ====================================================================
>
>
> ====================================================================
> == main program: ==
> ====================================================================
> }}}
<eucode>
>
> include get.e
> include graphics.e
> include banking.e
>
> sequence myAccount, null_status
>
> text_color(WHITE) bk_color(BLUE)
> clear_screen()
>
> myAccount = BankProgram({"new"})
> myAccount = BankProgram({"Deposit", myAccount, 12000.00})
> myAccount = BankProgram({"Withdrawal", myAccount, 150.00})
> null_status = BankProgram({"Balance", myAccount})
>
> </eucode>
{{{
>
> Other functions and features can be added from this basic
> framework. Features such as checking for overdraft status, adding
> extra fees, crediting or debiting accounts, etc.
This is the sort of hack you are unfortunately saddled with when using the
language. Removing this sort of global namespace pollution is a priority
issue IMHO.
If only because, once you have defined a constant "balance" to number the
relevant field in your sequence, you can no longer have another "structure"
use the same name, as the field index name must be global. This makes no
sense.
CChris
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