Comment and add MEM function to REPL

src/lisp/drawl.pla

@@ -40,9 +40,11 @@ import sexpr
   predef parse_expr(evalptr, level, refill)#2
   predef eval_expr(expr)#1
   predef eval_num(expr)#2
-  predef bool_pred(bool)
+  predef bool_pred(bool)#1
+  predef new_cons#1
+  predef new_int(intlo, inthi)#1
+  predef new_sym(symstr)#1
   predef new_assoc(symptr, valptr)#0
-  predef install_natv(symstr, funcptr)#0
 end
 
 //
@@ -58,7 +60,7 @@ var fileref, filebuf  // file read vars
 byte quit = FALSE     // quit interpreter flag
 
 //
-// Native function to exit REPL
+// Native functions
 //
 
 def natv_bye(expr)
@@ -66,6 +68,14 @@ def natv_bye(expr)
   return NULL // Quick exit from REPL
 end
 
+def natv_memavail(expr)
+  return new_int(heapavail, 0)
+end
+
+//
+// Keyboard and file input routines
+//
+
 def refill_keybd
   var readline
 
@@ -127,6 +137,10 @@ def read_file
   return expr
 end
 
+//
+// Handle command line options
+//
+
 def parse_cmdline#0
   var filename
 
@@ -143,10 +157,16 @@ def parse_cmdline#0
   fin
 end
 
+//
+// REPL
+//
+
 parse_cmdline
-install_natv("BYE", @natv_bye)
+new_sym("BYE")=>natv = @natv_bye)
+new_sym("MEM")=>natv = @natv_memavail)
 while not quit
   putln; print_expr(eval_expr(readfn()))
   gc_trigger--; if gc_trigger == 0; gc; gc_trigger = GC_RESET; fin
 loop
+puts("\nGoodbye!\n")
 done

src/lisp/s-expr.pla

@@ -128,7 +128,7 @@ end
 // Build ATOMS
 //
 
-def new_cons
+export def new_cons#1
   var consptr
 
   if cons_free
@@ -162,7 +162,7 @@ def match_int(intlo, inthi)
   return NULL
 end
 
-def new_int(intlo, inthi)
+export def new_int(intlo, inthi)#1
   var intptr
 
   intptr = match_int(intlo, inthi)
@@ -208,7 +208,7 @@ def match_sym(symstr)
   return NULL
 end
 
-def new_sym(symstr)
+export def new_sym(symstr)#1
   var symptr
 
   symptr = match_sym(symstr)
@@ -750,10 +750,6 @@ end
 // Install default functions
 //
 
-export def install_natv(symstr, funcptr)#0
-  new_sym(symstr)=>natv = funcptr)
-end
-
 new_assoc(new_sym("NIL"), NULL)
 new_assoc(new_sym("T"),   @pred_true)
 new_assoc(new_sym("F"),   @pred_false)