Skip to content

Commit

Permalink
Implement suggestions from issue kanaka#587 in stepA of several langu…
Browse files Browse the repository at this point in the history 
…ages

* Merge eval-ast and eval into a single conditional.

* Print "EVAL: $ast" at the top of EVAL.

* Expand macros during the apply phase, removing lots of duplicate
  tests, and increasing the overall consistency by allowing the macro
  to be computed instead of referenced by name (`((defmacro! cond
  (...)))` is currently illegal for example).

Each change was already applied by some implementations.

With the two last changes, macroexpand and quasiquoteexpand special
forms are not needed anymore.

If macroexpand is kept:

* an optional test should be added for `(macroexpand ())`, which
  currently fails on several implementations,

* it should only apply one macro at a time.  The purpose being
  debugging, hiding an iteration does not help.  Moreover, the loop is
  currently untested (and probably wrong in nim).

These tests fail:

* objpascal: I have no such error with a more recent compiler

* groovy: stack overflow during test of recursive functions.
  Did work after first push.

* elm: most probably unrelated, this directory is unchanged
  • Loading branch information
@asarhaddon
asarhaddon committed Sep 29, 2021
1 parent 1c76e85 commit 3dad5f7
Show file tree
Hide file tree
Showing 55 changed files with 1,347 additions and 2,981 deletions.
37 changes: 5 additions & 32 deletions impls/ada.2/stepa_mal.adb
View file
Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,6 @@ procedure StepA_Mal is
-- True when the environment has been created in this recursion
-- level, and has not yet been referenced by a closure. If so,
-- we can reuse it instead of creating a subenvironment.
Macroexpanding : Boolean := False;
First : Types.T;
begin
<<Restart>>
Expand Down Expand Up @@ -184,14 +183,6 @@ procedure StepA_Mal is
Ast => Ast.Sequence.all.Data (3),
Env => Env));
end;
elsif First.Str.all = "macroexpand" then
Err.Check (Ast.Sequence.all.Length = 2, "expected 1 parameter");
Macroexpanding := True;
Ast := Ast.Sequence.all.Data (2);
goto Restart;
elsif First.Str.all = "quasiquoteexpand" then
Err.Check (Ast.Sequence.all.Length = 2, "expected 1 parameter");
return Quasiquote (Ast.Sequence.all.Data (2));
elsif First.Str.all = "quasiquote" then
Err.Check (Ast.Sequence.all.Length = 2, "expected 1 parameter");
Ast := Quasiquote (Ast.Sequence.all.Data (2));
Expand Down Expand Up @@ -248,24 +239,10 @@ procedure StepA_Mal is
case First.Kind is
when Kind_Macro =>
-- Use the unevaluated arguments.
if Macroexpanding then
-- Evaluate the macro with tail call optimization.
if not Env_Reusable then
Env := Envs.New_Env (Outer => First.Fn.all.Env);
Env_Reusable := True;
end if;
Env.all.Set_Binds
(Binds => First.Fn.all.Params.all.Data,
Exprs => Ast.Sequence.all.Data (2 .. Ast.Sequence.all.Length));
Ast := First.Fn.all.Ast;
goto Restart;
else
-- Evaluate the macro normally.
Ast := First.Fn.all.Apply
(Ast.Sequence.all.Data (2 .. Ast.Sequence.all.Length));
-- Then evaluate the result with TCO.
goto Restart;
end if;
Ast := First.Fn.all.Apply
(Ast.Sequence.all.Data (2 .. Ast.Sequence.all.Length));
-- Then evaluate the result with TCO.
goto Restart;
when Types.Kind_Function =>
null;
when others =>
Expand Down Expand Up @@ -296,11 +273,7 @@ procedure StepA_Mal is
end;
exception
when Err.Error =>
if Macroexpanding then
Err.Add_Trace_Line ("macroexpand", Ast);
else
Err.Add_Trace_Line ("eval", Ast);
end if;
Err.Add_Trace_Line ("eval", Ast);
raise;
end Eval;

Expand Down
159 changes: 44 additions & 115 deletions impls/ada/stepa_mal.adb
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,54 +55,6 @@ procedure StepA_Mal is
return Res;
end Def_Macro;


function Macro_Expand (Ast : Mal_Handle; Env : Envs.Env_Handle)
return Mal_Handle is
Res : Mal_Handle;
E : Envs.Env_Handle;
LMT : List_Mal_Type;
LP : Lambda_Ptr;
begin

Res := Ast;
E := Env;

loop

if Deref (Res).Sym_Type /= List then
exit;
end if;

LMT := Deref_List (Res).all;

-- Get the macro in the list from the env
-- or return null if not applicable.
LP := Get_Macro (Res, E);

exit when LP = null or else not LP.Get_Is_Macro;

declare
Fn_List : Mal_Handle := Cdr (LMT);
Params : List_Mal_Type;
begin
E := Envs.New_Env (E);

Params := Deref_List (LP.Get_Params).all;
if Envs.Bind (E, Params, Deref_List (Fn_List).all) then

Res := Eval (LP.Get_Expr, E);

end if;

end;

end loop;

return Res;

end Macro_Expand;


function Eval_As_Boolean (MH : Mal_Handle) return Boolean is
Res : Boolean;
begin
Expand All @@ -125,45 +77,6 @@ procedure StepA_Mal is
end Eval_As_Boolean;


function Eval_Ast
(Ast : Mal_Handle; Env : Envs.Env_Handle)
return Mal_Handle is

function Call_Eval (A : Mal_Handle) return Mal_Handle is
begin
return Eval (A, Env);
end Call_Eval;

begin

case Deref (Ast).Sym_Type is

when Sym =>

declare
Sym : Mal_String := Deref_Sym (Ast).Get_Sym;
begin
-- if keyword, return it. Otherwise look it up in the environment.
if Sym(1) = ':' then
return Ast;
else
return Envs.Get (Env, Sym);
end if;
exception
when Envs.Not_Found =>
raise Envs.Not_Found with ("'" & Sym & "' not found");
end;

when List =>

return Map (Call_Eval'Unrestricted_Access, Deref_List_Class (Ast).all);

when others => return Ast;

end case;

end Eval_Ast;

function Starts_With (Ast : Mal_Handle; Symbol : String) return Boolean is
A0 : Mal_Handle;
begin
Expand Down Expand Up @@ -273,6 +186,12 @@ procedure StepA_Mal is
Env : Envs.Env_Handle;
First_Param, Rest_Params : Mal_Handle;
Rest_List, Param_List : List_Mal_Type;

function Call_Eval (A : Mal_Handle) return Mal_Handle is
begin
return Eval (A, Env);
end Call_Eval;

begin

Param := AParam;
Expand All @@ -284,14 +203,30 @@ procedure StepA_Mal is
Ada.Text_IO.Put_Line ("Evaling " & Deref (Param).To_String);
end if;

Param := Macro_Expand (Param, Env);
case Deref (Param).Sym_Type is
when Sym =>

if Debug then
Ada.Text_IO.Put_Line ("After expansion " & Deref (Param).To_String);
end if;
declare
Sym : Mal_String := Deref_Sym (Param).Get_Sym;
begin
-- if keyword, return it. Otherwise look it up in the environment.
if Sym(1) = ':' then
return Param;
else
return Envs.Get (Env, Sym);
end if;
exception
when Envs.Not_Found =>
raise Envs.Not_Found with ("'" & Sym & "' not found");
end;

if Deref (Param).Sym_Type = List and then
Deref_List (Param).Get_List_Type = List_List then
when List =>
case Deref_List (Param).Get_List_Type is
when Hashed_List | Vector_List =>

return Map (Call_Eval'Unrestricted_Access, Deref_List_Class (Param).all);

when List_List =>

Param_List := Deref_List (Param).all;

Expand All @@ -310,9 +245,6 @@ procedure StepA_Mal is
elsif Deref (First_Param).Sym_Type = Sym and then
Deref_Sym (First_Param).Get_Sym = "defmacro!" then
return Def_Macro (Rest_List, Env);
elsif Deref (First_Param).Sym_Type = Sym and then
Deref_Sym (First_Param).Get_Sym = "macroexpand" then
return Macro_Expand (Car (Rest_List), Env);
elsif Deref (First_Param).Sym_Type = Sym and then
Deref_Sym (First_Param).Get_Sym = "let*" then
declare
Expand Down Expand Up @@ -407,11 +339,6 @@ procedure StepA_Mal is

return Car (Rest_List);

elsif Deref (First_Param).Sym_Type = Sym and then
Deref_Sym (First_Param).Get_Sym = "quasiquoteexpand" then

return Quasi_Quote_Processing (Car (Rest_List));

elsif Deref (First_Param).Sym_Type = Sym and then
Deref_Sym (First_Param).Get_Sym = "quasiquote" then

Expand Down Expand Up @@ -448,18 +375,11 @@ procedure StepA_Mal is
else

-- The APPLY section.
declare
Evaled_H : Mal_Handle;
begin
Evaled_H := Eval_Ast (Param, Env);

Param_List := Deref_List (Evaled_H).all;

First_Param := Car (Param_List);
Rest_Params := Cdr (Param_List);
Rest_List := Deref_List (Rest_Params).all;
First_Param := Eval (First_Param, Env);

if Deref (First_Param).Sym_Type = Func then
Rest_Params := Map (Call_Eval'Unrestricted_Access, Rest_List);
return Call_Func (Deref_Func (First_Param).all, Rest_Params);
elsif Deref (First_Param).Sym_Type = Lambda then
declare
Expand All @@ -472,6 +392,16 @@ procedure StepA_Mal is
begin

L := Deref_Lambda (First_Param).all;

if L.Get_Is_Macro then
-- Apply to *unevaluated* arguments
Param := L.Apply (Rest_Params);
-- then EVAL the result.
goto Tail_Call_Opt;
end if;

Rest_Params := Map (Call_Eval'Unrestricted_Access, Rest_List);

E := Envs.New_Env (L.Get_Env);

Param_Names := Deref_List (L.Get_Params).all;
Expand All @@ -495,15 +425,14 @@ procedure StepA_Mal is
raise Runtime_Exception with "Deref called on non-Func/Lambda";
end if;

end;

end if;

else -- not a List_List
end case;
when others => -- not a list, map, symbol or vector

return Eval_Ast (Param, Env);
return Param;

end if;
end case;

end Eval;

Expand Down
Loading

0 comments on commit 3dad5f7

Please sign in to comment.