From d2101dbd473eff0984e540bd76b45cd4484803ff Mon Sep 17 00:00:00 2001
From: Simon Brooke <simon@journeyman.cc>
Date: Sat, 24 Jul 2021 08:54:55 +0100
Subject: [PATCH] Started to try to get back into this; work on exceptions and
loops.
---
.vscode/settings.json | 7 ++++
src/memory/conspage.c | 2 +-
src/memory/consspaceobject.c | 2 +-
src/memory/consspaceobject.h | 25 +++++++++++---
src/memory/stack.c | 3 +-
src/ops/exceptions.c | 62 +++++++++++++++++++++++++++++++++++
src/ops/lispops.c | 6 ++--
src/ops/lispops.h | 4 +++
utils_src/tagvalcalc/tvc | Bin 8544 -> 16848 bytes
9 files changed, 101 insertions(+), 10 deletions(-)
create mode 100644 .vscode/settings.json
create mode 100644 src/ops/exceptions.c
diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..14fb483
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,7 @@
+{
+ "files.associations": {
+ "future": "cpp",
+ "system_error": "cpp",
+ "functional": "c"
+ }
+}
\ No newline at end of file
diff --git a/src/memory/conspage.c b/src/memory/conspage.c
index 2d0958d..53496d3 100644
--- a/src/memory/conspage.c
+++ b/src/memory/conspage.c
@@ -148,7 +148,7 @@ void free_cell( struct cons_pointer pointer ) {
dec_ref( cell->payload.cons.cdr );
break;
case EXCEPTIONTV:
- dec_ref( cell->payload.exception.message );
+ dec_ref( cell->payload.exception.payload );
dec_ref( cell->payload.exception.frame );
break;
case FUNCTIONTV:
diff --git a/src/memory/consspaceobject.c b/src/memory/consspaceobject.c
index 344f4ae..98bb495 100644
--- a/src/memory/consspaceobject.c
+++ b/src/memory/consspaceobject.c
@@ -163,7 +163,7 @@ struct cons_pointer make_exception( struct cons_pointer message,
inc_ref( message );
inc_ref( frame_pointer );
- cell->payload.exception.message = message;
+ cell->payload.exception.payload = message;
cell->payload.exception.frame = frame_pointer;
result = pointer;
diff --git a/src/memory/consspaceobject.h b/src/memory/consspaceobject.h
index 9197172..4b0500b 100644
--- a/src/memory/consspaceobject.h
+++ b/src/memory/consspaceobject.h
@@ -45,7 +45,8 @@
#define CONSTV 1397641027
/**
- * An exception.
+ * An exception. TODO: we need a means of dealing with different classes of
+ * exception, and we don't have one yet.
*/
#define EXCEPTIONTAG "EXEP"
@@ -108,6 +109,17 @@
*/
#define LAMBDATV 1094995276
+/**
+ * A loop exit is a special kind of exception which has exactly the same
+ * payload as an exception.
+ */
+#define LOOPXTAG "LOOX"
+
+/**
+ * The string `LOOX`, considered as an `unsigned int`.
+ */
+#define LOOPXTV 1481592652
+
/**
* The special cons cell at address {0,0} whose car and cdr both point to
* itself.
@@ -286,10 +298,15 @@
#define keywordp(conspoint) (check_tag(conspoint,KEYTAG))
/**
- * true if `conspoint` points to a special Lambda cell, else false
+ * true if `conspoint` points to a Lambda binding cell, else false
*/
#define lambdap(conspoint) (check_tag(conspoint,LAMBDATAG))
+/**
+ * true if `conspoint` points to a loop exit exception, else false.
+ */
+#define loopexitp(conspoint) (check_tag(conspoint,LOOPXTAG))
+
/**
* true if `conspoint` points to a special form cell, else false
*/
@@ -414,8 +431,8 @@ struct cons_payload {
* Message should be a Lisp string; frame should be a pointer to an (unfreed) stack frame.
*/
struct exception_payload {
- /** The message: should be a Lisp string but in practice anything printable will do. */
- struct cons_pointer message;
+ /** The payload: usually a Lisp string but in practice anything printable will do. */
+ struct cons_pointer payload;
/** pointer to the (unfreed) stack frame in which the exception was thrown. */
struct cons_pointer frame;
};
diff --git a/src/memory/stack.c b/src/memory/stack.c
index 3f4a271..d6d3c36 100644
--- a/src/memory/stack.c
+++ b/src/memory/stack.c
@@ -267,7 +267,8 @@ void dump_frame( URL_FILE * output, struct cons_pointer frame_pointer ) {
void dump_stack_trace( URL_FILE * output, struct cons_pointer pointer ) {
if ( exceptionp( pointer ) ) {
- print( output, pointer2cell( pointer ).payload.exception.message );
+ // todo: if the payload isn't a message, we maybe shouldn't print it?
+ print( output, pointer2cell( pointer ).payload.exception.payload );
url_fputws( L"\n", output );
dump_stack_trace( output,
pointer2cell( pointer ).payload.exception.frame );
diff --git a/src/ops/exceptions.c b/src/ops/exceptions.c
new file mode 100644
index 0000000..48c031f
--- /dev/null
+++ b/src/ops/exceptions.c
@@ -0,0 +1,62 @@
+ /*
+ * exceptions.c
+ *
+ * This is really, really unfinished and doesn't yet work. One of the really key
+ * things about exceptions is that the stack frames between the throw and the
+ * catch should not be derefed, so eval/apply will need to be substantially
+ * re-written.
+ *
+ * (c) 2021 Simon Brooke <simon@journeyman.cc>
+ * Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include <ctype.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "consspaceobject.h"
+#include "conspage.h"
+#include "debug.h"
+#include "dump.h"
+#include "equal.h"
+#include "integer.h"
+#include "intern.h"
+#include "io.h"
+#include "lispops.h"
+#include "map.h"
+#include "print.h"
+#include "read.h"
+#include "stack.h"
+#include "vectorspace.h"
+
+
+/**
+ * OK, the idea here (and I know this is less than perfect) is that the basic `try`
+ * function in PSSE takes two arguments, the first, `body`, being a list of forms,
+ * and the second, `catch`, being a catch handler (which is also a list of forms).
+ * Forms from `body` are evaluated in turn until one returns an exception object,
+ * or until the list is exhausted. If the list was exhausted, then the value of
+ * evaluating the last form in `body` is returned. If an exception was encountered,
+ * then each of the forms in `catch` is evaluated and the value of the last of
+ * those is returned.
+ *
+ * This is experimental. It almost certainly WILL change.
+ */
+struct cons_pointer lisp_try(struct stack_frame *frame,
+ struct cons_pointer frame_pointer,
+ struct cons_pointer env)
+{
+ struct cons_pointer result = c_progn(frame, frame_pointer, frame->arg[0], env);
+
+ if (loopexitp(result))
+ {
+ // TODO: need to put the exception into the environment!
+ result = c_progn(frame, frame_pointer, frame->arg[1], env);
+ }
+
+ return result;
+}
+
+
diff --git a/src/ops/lispops.c b/src/ops/lispops.c
index 4e2ddbf..8dd0109 100644
--- a/src/ops/lispops.c
+++ b/src/ops/lispops.c
@@ -107,7 +107,7 @@ struct cons_pointer eval_forms( struct stack_frame *frame,
list = c_cdr( list );
}
- return result;
+ return c_reverse( result);
}
/**
@@ -991,7 +991,7 @@ c_progn( struct stack_frame *frame, struct cons_pointer frame_pointer,
result = eval_form( frame, frame_pointer, c_car( expressions ), env );
dec_ref( r );
- expressions = c_cdr( expressions );
+ expressions = exceptionp(result) ? NIL : c_cdr( expressions );
}
return result;
@@ -1259,7 +1259,7 @@ struct cons_pointer lisp_source( struct stack_frame *frame,
case SPECIALTV:
result = c_assoc( source_key, cell.payload.special.meta );
break;
- case LAMBDATV:
+ case LAMBDATV:
result = make_cons( c_string_to_lisp_symbol( L"lambda" ),
make_cons( cell.payload.lambda.args,
cell.payload.lambda.body ) );
diff --git a/src/ops/lispops.h b/src/ops/lispops.h
index 122635f..f359252 100644
--- a/src/ops/lispops.h
+++ b/src/ops/lispops.h
@@ -29,6 +29,10 @@
struct cons_pointer c_reverse( struct cons_pointer arg );
+struct cons_pointer
+c_progn( struct stack_frame *frame, struct cons_pointer frame_pointer,
+ struct cons_pointer expressions, struct cons_pointer env );
+
/**
* Useful building block; evaluate this single form in the context of this
* parent stack frame and this environment.
diff --git a/utils_src/tagvalcalc/tvc b/utils_src/tagvalcalc/tvc
index a639364e1d9b231bea94f83e58fdd6378dcccd83..acd850a02231fc7f80d1516dc01c995fcc0d848b 100755
GIT binary patch
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