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mal/impls/ada.2/err.ads
Joel Martin 8a19f60386 Move implementations into impls/ dir
- Reorder README to have implementation list after "learning tool"
  bullet.

- This also moves tests/ and libs/ into impls. It would be preferrable
  to have these directories at the top level.  However, this causes
  difficulties with the wasm implementations which need pre-open
  directories and have trouble with paths starting with "../../". So
  in lieu of that, symlink those directories to the top-level.

- Move the run_argv_test.sh script into the tests directory for
  general hygiene.
2020-02-10 23:50:16 -06:00

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1.5 KiB
Ada

with Ada.Exceptions;
with Ada.Strings.Unbounded;
with Types;
-- We declare a variable of type Types.T.
pragma Elaborate (Types);
package Err is
-- Error handling.
-- Built-in function.
function Throw (Args : in Types.T_Array) return Types.T;
-- Ada exceptions can only carry an immutable String in each
-- occurence, so we require a global variable to store the last
-- exception as a Mal object anyway, and may as well use it for
-- simple string messages.
Error : exception;
Data : Types.T;
Trace : Ada.Strings.Unbounded.Unbounded_String;
-- Convenient shortcuts.
procedure Raise_With (Message : in String) with No_Return;
-- Similar to a "raise with Message" Ada statement.
-- Store the message into Data,
-- store the message and "Uncaught exception: " into Trace,
-- then raise Error.
procedure Raise_In_Mal (E : in Ada.Exceptions.Exception_Occurrence)
with No_Return;
-- Raise_With (Ada.Exceptions.Exception_Information (E))
procedure Add_Trace_Line (Action : in String;
Ast : in Types.T);
-- Appends a line like "Action: Ast" to Trace.
procedure Check (Condition : in Boolean;
Message : in String) with Inline;
-- Raise_With if Condition fails.
-- It is probably more efficient to construct a boolean and call
-- this procedure once, as "inline" is only a recommendation.
-- Beware of the classical performance issue that the Message is
-- formatted even if the Condition does not hold.
end Err;