Index: class.c
==================================================================
--- class.c
+++ class.c
@@ -142,10 +142,11 @@
 #define MAC_VERSION 0xFFE0
 #define MAC_DEFINE 0xFFE1
 #define MAC_INCLUDE 0xFFE2
 #define MAC_CALL 0xFFE3
 #define MAC_APPEND 0xFFE4
+#define MAC_EDIT 0xFFE5
 #define MAC_UNDEFINED 0xFFFF
 
 static TokenList*add_macro(void) {
   TokenList*o=malloc(sizeof(TokenList));
   if(!o) fatal("Allocation failed\n");
@@ -619,10 +620,11 @@
   MacroStack*ms=malloc(sizeof(MacroStack));
   TokenList**ap=0;
   int a=0;
   int b=0;
   int c=0;
+  if(StackProtection()) fatal("Stack overflow\n");
   ref_macro(mac);
   if(!ms) fatal("Allocation failed\n");
   ms->tok=mac;
   ms->n=0;
   ms->args=0;
@@ -995,17 +997,46 @@
           }
           nxttok();
           if(!(tokent&TF_NAME) || tokenv!=OP_STRING) ParseError("String literal expected\n");
           define_macro(look_hash_mac(),0);
           goto again;
+        case MAC_EDIT:
+          if(!macros) ParseError("Cannot edit nonexistent macro\n");
+          nxttok();
+          if(!(tokent&TF_NAME) || tokenv!=OP_STRING) ParseError("String literal expected\n");
+          n=glohash[look_hash_mac()].id;
+          if(n<0xC000 || n>MAX_MACRO+0xC000-1 || !macros[n-0xC000]) ParseError("Undefined macro: {%s}\n",tokenstr);
+          nxttok();
+          n-=0xC000;
+          if(macros[n]->t&(TF_MACRO|TF_EOF)) ParseError("Invalid edit token\n");
+          free(macros[n]->str);
+          macros[n]->t=tokent;
+          macros[n]->v=tokenv;
+          macros[n]->str=0;
+          if(*tokenstr) {
+            macros[n]->str=strdup(tokenstr);
+            if(!macros[n]->str) fatal("Allocation failed\n");
+          }
+          if(main_options['M']) {
+            int i;
+            printf("M= @%4d %04X %08X \"",linenum,tokent,tokenv);
+            for(i=0;tokenstr[i];i++) {
+              if(tokenstr[i]<32 || tokenstr[i]>126) printf("<%02X>",tokenstr[i]&255);
+              else putchar(tokenstr[i]);
+            }
+            printf("\"\n");
+          }
+          nxttok();
+          if(tokent!=TF_MACRO+TF_CLOSE) ParseError("Too many macro arguments\n");
+          goto again;
         case MAC_UNDEFINED:
           ParseError("Undefined macro: {%s}\n",tokenstr);
           break;
         default:
           ParseError("Strange macro token: 0x%04X\n",glohash[tokenv].id);
       }
-      if(main_options['M']) printf("M-\n");
+      if(main_options['M']) printf("M- %5d %04X %08X\n",linenum,tokent,tokenv);
     }
   }
 }
 
 static int pool_string(const char*s) {
@@ -2098,10 +2129,11 @@
   strcpy(tokenstr,"version"); glohash[look_hash_mac()].id=MAC_VERSION;
   strcpy(tokenstr,"define"); glohash[look_hash_mac()].id=MAC_DEFINE;
   strcpy(tokenstr,"include"); glohash[look_hash_mac()].id=MAC_INCLUDE;
   strcpy(tokenstr,"call"); glohash[look_hash_mac()].id=MAC_CALL;
   strcpy(tokenstr,"append"); glohash[look_hash_mac()].id=MAC_APPEND;
+  strcpy(tokenstr,"edit"); glohash[look_hash_mac()].id=MAC_EDIT;
   if(main_options['L']) {
     for(;;) {
       nxttok();
       printf("** %5d %04X %08X \"",linenum,tokent,tokenv);
       for(i=0;tokenstr[i];i++) {

Index: class.doc
==================================================================
--- class.doc
+++ class.doc
@@ -168,10 +168,16 @@
   expanded during each use. A macro argument token with a single backslash
   expands to the argument in that position, while a macro argument tokens
   with multiple tokens becomes the token with one less backslash. It is
   permitted to redefine existing macros as well as new ones.
 
+{edit <string> <token>}
+  Edit a macro. This changes the first token of the definition of the macro
+  (which must not be another macro) to the specified token (which also must
+  not be another macro). The token is expanded, and must be a single token
+  once it is expanded; that is what it will be replaced with.
+
 {include <string>}
   Include text from another file into this one. You cannot use {include}
   inside of another macro or in a macro argument.
 
 {make <mode> <arg>}