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step7_quote.pas
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264 lines (242 loc) Β· 6.53 KB
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program Mal;
{$H+} // Use AnsiString
Uses sysutils,
CMem,
fgl,
math,
mal_readline,
mal_types,
mal_func,
reader,
printer,
mal_env,
core;
var
Repl_Env : TEnv;
Line : string;
I : longint;
Key : string;
CmdArgs : TMalArray;
// read
function READ(const Str: string) : TMal;
begin
READ := read_str(Str);
end;
// eval
function is_pair(x: TMal) : Boolean;
begin
is_pair := _sequential_Q(x) and (Length((x as TMalList).Val) > 0);
end;
function quasiquote(Ast: TMal) : TMal;
var
Arr, Arr0 : TMalArray;
A0, A00 : TMal;
begin
if not is_pair(Ast) then
Exit(_list(TMalSymbol.Create('quote'), Ast))
else
begin
Arr := (Ast as TMalList).Val;
A0 := Arr[0];
if (A0 is TMalSymbol) and
((A0 as TMalSymbol).Val = 'unquote') then
Exit(Arr[1])
else if is_pair(A0) then
begin
Arr0 := (Arr[0] as TMalList).Val;
A00 := Arr0[0];
if (A00 is TMalSymbol) and
((A00 as TMalSymbol).Val = 'splice-unquote') then
Exit(_list(TMalSymbol.Create('concat'),
Arr0[1],
quasiquote((Ast as TMalList).Rest)));
end;
quasiquote := _list(TMalSymbol.Create('cons'),
quasiquote(A0),
quasiquote((Ast as TMalList).Rest));
end;
end;
// Forward declation since eval_ast call it
function EVAL(Ast: TMal; Env: TEnv) : TMal; forward;
function eval_ast(Ast: TMal; Env: TEnv) : TMal;
var
OldArr, NewArr : TMalArray;
OldDict, NewDict : TMalDict;
I : longint;
begin
if Ast is TMalSymbol then
begin
eval_ast := Env.Get((Ast as TMalSymbol));
end
else if Ast is TMalList then
begin
OldArr := (Ast as TMalList).Val;
SetLength(NewArr, Length(OldArr));
for I := 0 to Length(OldArr)-1 do
begin
NewArr[I] := EVAL(OldArr[I], Env);
end;
if Ast is TMalVector then
eval_ast := TMalVector.Create(NewArr)
else
eval_ast := TMalList.Create(NewArr);
end
else if Ast is TMalHashMap then
begin
OldDict := (Ast as TMalHashMap).Val;
NewDict := TMalDict.Create;
I := 0;
while I < OldDict.Count do
begin
NewDict[OldDict.Keys[I]] := EVAL(OldDict[OldDict.Keys[I]], Env);
I := I + 1;
end;
eval_ast := TMalHashMap.Create(NewDict);
end
else
eval_ast := Ast;
end;
function EVAL(Ast: TMal; Env: TEnv) : TMal;
var
Lst : TMalList;
Arr : TMalArray;
Arr1 : TMalArray;
A0Sym : string;
LetEnv : TEnv;
Cond : TMal;
I : longint;
Fn : TMalFunc;
Args : TMalArray;
begin
while true do
begin
if Ast.ClassType <> TMalList then
Exit(eval_ast(Ast, Env));
// Apply list
Lst := (Ast as TMalList);
Arr := Lst.Val;
if Length(Arr) = 0 then
Exit(Ast);
if Arr[0] is TMalSymbol then
A0Sym := (Arr[0] as TMalSymbol).Val
else
A0Sym := '__<*fn*>__';
case A0Sym of
'def!':
Exit(Env.Add((Arr[1] as TMalSymbol), EVAL(Arr[2], ENV)));
'let*':
begin
LetEnv := TEnv.Create(Env);
Arr1 := (Arr[1] as TMalList).Val;
I := 0;
while I < Length(Arr1) do
begin
LetEnv.Add((Arr1[I] as TMalSymbol), EVAL(Arr1[I+1], LetEnv));
Inc(I,2);
end;
Env := LetEnv;
Ast := Arr[2]; // TCO
end;
'quote':
Exit(Arr[1]);
'quasiquote':
Ast := quasiquote(Arr[1]);
'do':
begin
eval_ast(TMalList.Create(copy(Arr,1, Length(Arr)-2)), Env);
Ast := Arr[Length(Arr)-1]; // TCO
end;
'if':
begin
Cond := EVAL(Arr[1], Env);
if (Cond is TMalNil) or (Cond is TMalFalse) then
if Length(Arr) > 3 then
Ast := Arr[3] // TCO
else
Exit(TMalNil.Create)
else
Ast := Arr[2]; // TCO
end;
'fn*':
begin
Exit(TMalFunc.Create(Arr[2], Env, (Arr[1] as TMalList)));
end;
else
begin
Arr := (eval_ast(Ast, Env) as TMalList).Val;
if Arr[0] is TMalFunc then
begin
Fn := Arr[0] as TMalFunc;
if Length(Arr) < 2 then
SetLength(Args, 0)
else
Args := copy(Arr, 1, Length(Arr)-1);
if Fn.Ast = nil then
Exit(Fn.Val(Args))
else
begin
Env := TEnv.Create(Fn.Env, Fn.Params, Args);
Ast := Fn.Ast; // TCO
end
end
else
raise Exception.Create('invalid apply');
end;
end;
end;
end;
// print
function PRINT(Exp: TMal) : string;
begin
PRINT := pr_str(Exp, True);
end;
// repl
function REP(Str: string) : string;
begin
REP := PRINT(EVAL(READ(Str), Repl_Env));
end;
function do_eval(Args : TMalArray) : TMal;
begin
do_eval := EVAL(Args[0], Repl_Env);
end;
begin
Repl_Env := TEnv.Create;
core.EVAL := @EVAL;
// core.pas: defined using Pascal
for I := 0 to core.NS.Count-1 do
begin
Key := core.NS.Keys[I];
Repl_Env.Add(TMalSymbol.Create(Key),
TMalFunc.Create(core.NS[Key]));
end;
Repl_Env.Add(TMalSymbol.Create('eval'), TMalFunc.Create(@do_eval));
SetLength(CmdArgs, Max(0, ParamCount-1));
for I := 2 to ParamCount do
CmdArgs[I-2] := TMalString.Create(ParamStr(I));
Repl_Env.Add(TMalSymbol.Create('*ARGV*'), TMalList.Create(CmdArgs));
// core.mal: defined using language itself
REP('(def! not (fn* (a) (if a false true)))');
REP('(def! load-file (fn* (f) (eval (read-string (str "(do " (slurp f) ")")))))');
if ParamCount >= 1 then
begin
REP('(load-file "' + ParamStr(1) + '")');
ExitCode := 0;
Exit;
end;
while True do
begin
try
Line := _readline('user> ');
if Line = '' then continue;
WriteLn(REP(Line))
except
On E : MalEOF do Halt(0);
On E : Exception do
begin
WriteLn('Error: ' + E.message);
WriteLn('Backtrace:');
WriteLn(GetBacktrace(E));
end;
end;
end;
end.