type My_Test_Type is (<>);
type My_Table_Type is array(My_Test_Type) of Integer;
When I try to use this code in the GNAT community IDE, I get this error:
ads:9:26: error: identifier expected
This is the line it's pointing to:
type My_Test_Type is (<>);
When I build the code in the legacy IDE, it compiles and runs fine.
Any ideas what is going on here?
I've tried this only on my local PC running GNAT Studio Community 2021 (20210423) hosted on x86_64-w64-mingw32.
The legacy system is a cross compiler for the Power PC. It's old.
Ok, Here is more context.
I took the above lines an created a package which I am building and running in GNAT Studio community addition.
Here is the my_generic.ads
package My_Generic is
generic
type My_Test_Type is (<>);
type My_Table_Type is array(My_Test_Type) of Integer;
--
My_Table : My_Table_Type;
procedure InitMyTable(My_Table : My_Table_Type);
end My_Generic;
Here is my_generic.adb
with GNAT.IO; use GNAT.IO;
package body My_Generic is
procedure InitMyTable (My_Table : My_Table_Type) is
begin
Put_Line("Entered InitMyTable");
for i in 1..1000 loop
My_Table(i) := i + 1000;
end loop;
null;
end InitMyTable;
end My_Generic;
Main is
--...
--...
InitMyTable_i = new InitMyTable(My_Test_Type => range 1..10);
begin
--...
--...
Put_Line ("Initializing My table (<>)");
InitMyTable_i;
end Main;
when I build I get
error: declaration expected on the line
"InitMyTable_i = new InitMyTable(My_Test_Type => range 1..10);"
I basically have no idea what is going on here. I've tried many different ways to get things to work.
Any of the docs I have found, including the ones suggested below, are not helpful.
I would like to define HTML response status code numbers as a type but disallow arithmetic operators because it wouldn't make sense for them.
type Status_Code is range 100 .. 599;
function "+" (Left, Right : Status_Code) return Status_Code is
begin
pragma Assert (1 = -1);
return Left + Right;
end;
The code snippet above on GNAT will give an error saying assertion will fail on runtime, but that is false when I add two of the numbers together. Is there a way to force a compiler error or at least a warning when arithmetic attempted on a type like this?
It uses a simple process which asks the user the number of days in the month and the starting day of the week. The program demonstrates the overloading of packages in Ada, enumerations, types, subtypes, and output.
Here is the algorithm for displaying the month:
Output the heading with the names of the days of the week.
Output the initial blanks.
Set day = the first day input by the user.
loop date in 1 to number_of_days_in_the_month
output(date)
if (day = Saturday) then
insert a new line
day = Sunday
else
day = next day
end
end loop
Here is the program written in Ada:
with text_IO; use text_io;
procedure month is
subtype month_days is positive range 1..31;
type week_days is (Sun,Mon,Tue,Wed,Thu,Fri,Sat);
package positive_io is new integer_io(positive);
use positive_io;
package day_io is new enumeration_io(week_days);
use day_io;
answer: character;
firstday: week_days;
numberofdays: month_days;
procedure get_number_of_days(nd: out month_days) is
begin
put("Enter the number of days in the month: ");
new_line;
get(nd);
skip_line;
end get_number_of_days;
procedure get_first_day(fd: out week_days) is
begin
put("Enter the first day of the new month: ");
put("e.g. Sun, Mon, etc.");
new_line;
get(fd);
skip_line;
end get_first_day;
procedure display_month(nd: in month_days; fd: in week_days) is
day: week_days := fd;
four_blanks: constant string := " ";
width : constant integer := 4;
begin
for day in week_days loop
put(' ');
put(day);
end loop;
new_line;
for blank_days in Mon..fd loop
put(four_blanks);
end loop;
for date in 1..nd loop
put(date,width);
if day = Sat then
day := Sun;
new_line;
else
day := week_days'succ(day);
end if;
end loop;
new_line;
end display_month;
begin
loop
get_number_of_days(numberofdays);
get_first_day(firstday);
display_month(numberofdays,firstday);
put("Do you wish to see another month? "); new_line;
put("yes(y) or no(n): "); new_line;
get(answer); skip_line;
exit when answer = 'n' or answer = 'N';
end loop;
end month;
You will notice on Line 9, the redefinition of the package enumeration_io to permit the output of the headings, and the input of the first day of the month in an intuitive manner. Also a subtype, month_days, is created on Line 5 of the program which helps ensure proper input by constraining the values allowed in month_days.
The program repeatedly prompts the user for information, and prints the associated month. Here is the programming running:
Enter the number of days in the month:
31
Enter the first day of the new month: e.g. Sun, Mon, etc.
Wed
SUN MON TUE WED THU FRI SAT
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31
Do you wish to see another month?
yes(y) or no(n):
n
What happens if the number of days entered by the user is outside the constraints set? The program will raise a constraint error of the form:
raised CONSTRAINT_ERROR : month.adb:19 range check failed
But this can be fixed by modifying the user input routines. Here is how the procedure get_number_of_days() has been fixed.
procedure get_number_of_days(nd: out month_days) is
monthlen : month_days;
begin
loop
begin
put("Enter the number of days in the month: ");
new_line;
get(monthlen);
skip_line;
if monthlen in 28..31 then
exit;
else
raise constraint_error;
end if;
exception
when others =>
skip_line;
put("Bad input. Enter a value between 28-31.");
new_line;
end;
end loop;
nd := monthlen;
end get_number_of_days;
On Lines 10-14 there is an if statement which determines if the input is valid. Input outside of the values 28-31 raises a constraint_error, but this time it is dealt with by the procedure on Lines 15-19 (instead of the system). If an exception is raised, then a message is output to the user, and in this case the loop iterates again. If the input is valid, the input loop is exited. This is a good example of how easy it is to deal with various exceptions in Ada. Here is a sample of the program running with invalid input:
Enter the number of days in the month:
42
Bad input. Enter a value between 28-31.
Enter the number of days in the month:
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