From d84883a4ce7e269c5d0ed9b39365006476ac9efd Mon Sep 17 00:00:00 2001
From: Mark Pizzolato <mark@infocomm.com>
Date: Wed, 1 Apr 2015 10:29:14 -0700
Subject: [PATCH] SCP: Add a special pseudo name "$" which is the value
 returned from the most recent EXAMINE command which can be used for  register
 (or memory) indirect EXAMINE commands.

To examine the instruction which the PC points at:
   sim> EXAMINE PC
   sim> EXAMINE -m $
---
 scp.c | 58 ++++++++++++++++++++++++++++++++++------------------------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/scp.c b/scp.c
index 2f84763c..c4736cfe 100644
--- a/scp.c
+++ b/scp.c
@@ -491,6 +491,7 @@ static int32 noqueue_time;
 volatile int32 stop_cpu = 0;
 static char **sim_argv;
 t_value *sim_eval = NULL;
+t_value sim_last_val;
 FILE *sim_log = NULL;                                   /* log file */
 FILEREF *sim_log_ref = NULL;                            /* log file file reference */
 FILE *sim_deb = NULL;                                   /* debug file */
@@ -696,6 +697,8 @@ static const char simh_help[] =
       "++                       but not including address+length\n"
       "++STATE                  all registers in the device\n"
       "++ALL                    all locations in the unit\n"
+      "++$                      the last value displayed by an EXAMINE command\n"
+      "                         interpreted as an address\n"
       "3Switches\n"
       " Switches can be used to control the format of display information:\n\n"
        /***************** 80 character line width template *************************/
@@ -6279,7 +6282,7 @@ for (rptr = lowr; rptr <= highr; rptr++) {
                 else
                     Fprintf (ofile, "%s[%d]-%s[%d]: same as above\n", rptr->name, val_start+1, rptr->name, idx-1);
                 }
-            last_val = val;
+            sim_last_val = last_val = val;
             val_start = idx;
             reason = ex_reg (ofile, val, flag, rptr, idx);
             if (reason != SCPE_OK)
@@ -6637,7 +6640,7 @@ for (i = 0, j = addr; i < sim_emax; i++, j = j + dptr->aincr) {
                 }
             }
         }
-    sim_eval[i] = sim_eval[i] & mask;
+    sim_last_val = sim_eval[i] = sim_eval[i] & mask;
     }
 if ((reason != SCPE_OK) && (i == 0))
     return reason;
@@ -7067,35 +7070,42 @@ const char *get_range (DEVICE *dptr, const char *cptr, t_addr *lo, t_addr *hi,
 {
 const char *tptr;
 
-if (max && strncmp (cptr, "ALL", strlen ("ALL")) == 0) { /* ALL? */
+if (max && strncmp (cptr, "ALL", strlen ("ALL")) == 0) {    /* ALL? */
     tptr = cptr + strlen ("ALL");
     *lo = 0;
     *hi = max;
     }
 else {
-    if (dptr && sim_vm_parse_addr)                      /* get low */
-        *lo = sim_vm_parse_addr (dptr, (char *)cptr, (char **)&tptr);
-    else *lo = (t_addr) strtotv (cptr, &tptr, rdx);
-    if (cptr == tptr)                                   /* error? */
-            return NULL;
-    if ((*tptr == '-') || (*tptr == ':')) {             /* range? */
-        cptr = tptr + 1;
-        if (dptr && sim_vm_parse_addr)                  /* get high */
-            *hi = sim_vm_parse_addr (dptr, (char *)cptr, (char **)&tptr);
-        else *hi = (t_addr) strtotv (cptr, &tptr, rdx);
-        if (cptr == tptr)
-            return NULL;
-        if (*lo > *hi)
-            return NULL;
+    if (strncmp (cptr, "$", strlen ("$")) == 0) {           /* $? */
+        tptr = cptr + strlen ("$");
+        *hi = *lo = (t_addr)sim_last_val;
         }
-    else if (*tptr == '/') {                            /* relative? */
-        cptr = tptr + 1;
-        *hi = (t_addr) strtotv (cptr, &tptr, rdx);      /* get high */
-        if ((cptr == tptr) || (*hi == 0))
-            return NULL;
-        *hi = *lo + *hi - 1;
+    else {
+        if (dptr && sim_vm_parse_addr)                      /* get low */
+            *lo = sim_vm_parse_addr (dptr, (char *)cptr, (char **)&tptr);
+        else
+            *lo = (t_addr) strtotv (cptr, &tptr, rdx);
+        if (cptr == tptr)                                   /* error? */
+                return NULL;
+        if ((*tptr == '-') || (*tptr == ':')) {             /* range? */
+            cptr = tptr + 1;
+            if (dptr && sim_vm_parse_addr)                  /* get high */
+                *hi = sim_vm_parse_addr (dptr, (char *)cptr, (char **)&tptr);
+            else *hi = (t_addr) strtotv (cptr, &tptr, rdx);
+            if (cptr == tptr)
+                return NULL;
+            if (*lo > *hi)
+                return NULL;
+            }
+        else if (*tptr == '/') {                            /* relative? */
+            cptr = tptr + 1;
+            *hi = (t_addr) strtotv (cptr, &tptr, rdx);      /* get high */
+            if ((cptr == tptr) || (*hi == 0))
+                return NULL;
+            *hi = *lo + *hi - 1;
+            }
+        else *hi = *lo;
         }
-    else *hi = *lo;
     }
 if (term && (*tptr++ != term))
     return NULL;