X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=src%2Fforth.jl;h=5ced825bc66efa788a37fa18c3203bcbd02c517e;hb=17a6eb2756a624fc2274b601c20977f3bc014a6e;hp=a115e48221200b5af56576cde1087f90ca66d325;hpb=a4a274445e7ddaa07b595814dfeb9f6ddb0ce95a;p=forth.jl.git

diff --git a/src/forth.jl b/src/forth.jl
index a115e48..5ced825 100644
--- a/src/forth.jl
+++ b/src/forth.jl
@@ -31,6 +31,7 @@ size_TIB = 1096  # Terminal input buffer size
 
 mem = Array{Int64,1}(size_mem)
 primitives = Array{Function,1}()
+primNames = Array{ASCIIString,1}()
 
 # Built-in variables
 
@@ -54,9 +55,8 @@ type Reg
     PSP::Int64  # Parameter/data stack pointer
     IP::Int64   # Instruction pointer
     W::Int64    # Working register
-    X::Int64    # Extra register
 end
-reg = Reg(mem[RSP0], mem[PSP0], 0, 0, 0)
+reg = Reg(mem[RSP0], mem[PSP0], 0, 0)
 
 # Stack manipulation
 
@@ -101,31 +101,65 @@ function popPS()
     return val
 end
 
+# Handy functions for adding/retrieving strings to/from memory.
+
+getString(addr::Int64, len::Int64) = ASCIIString([Char(c) for c in mem[addr:(addr+len-1)]])
+function putString(str::ASCIIString, addr::Int64)
+    mem[addr:(addr+length(str)-1)] = [Int64(c) for c in str]
+end
+
 # Primitive creation and calling functions
 
+function defPrim(f::Function; name="nameless")
+    push!(primitives, f)
+    push!(primNames, name)
+
+    return -length(primitives)
+end
+
+callPrim(addr::Int64) = primitives[-addr]()
+
+# Word creation
+
 function createHeader(name::AbstractString, flags::Int64)
     mem[mem[HERE]] = mem[LATEST]
     mem[LATEST] = mem[HERE]
     mem[HERE] += 1
 
-    mem[mem[HERE]] = length(name) + flags; mem[HERE] += 1
-    mem[mem[HERE]:(mem[HERE]+length(name)-1)] = [Int(c) for c in name]; mem[HERE] += length(name)
+    mem[mem[HERE]] = length(name) | flags; mem[HERE] += 1
+    putString(name, mem[HERE]); mem[HERE] += length(name)
 end
 
-function defPrim(name::AbstractString, f::Function; flags::Int64=0)
+function defPrimWord(name::AbstractString, f::Function; flags::Int64=0)
     createHeader(name, flags)
 
-    push!(primitives, f)
-    mem[mem[HERE]] = -length(primitives)
+    codeWordAddr = mem[HERE]
+    mem[codeWordAddr] = defPrim(f, name=name)
     mem[HERE] += 1
 
-    return -length(primitives)
+    return codeWordAddr
 end
 
-callPrim(addr::Int64) = primitives[-addr]()
+function defWord(name::AbstractString, wordAddrs::Array{Int64,1}; flags::Int64=0)
+    createHeader(name, flags)
+
+    addr = mem[HERE]
+    mem[mem[HERE]] = DOCOL
+    mem[HERE] += 1
+
+    for wordAddr in wordAddrs
+        mem[mem[HERE]] = wordAddr
+        mem[HERE] += 1
+    end
+
+    return addr
+end
+
+# Variable creation
 
 function defExistingVar(name::AbstractString, varAddr::Int64; flags::Int64=0)
-    defPrim(name, eval(:(() -> begin
+
+    defPrimWord(name, eval(:(() -> begin
         pushPS($(varAddr))
         return NEXT
     end)))
@@ -134,20 +168,22 @@ end
 function defNewVar(name::AbstractString, initial::Int64; flags::Int64=0)
     createHeader(name, flags)
     
+    codeWordAddr = mem[HERE]
     varAddr = mem[HERE] + 1
-    push!(primitives, eval(:(() -> begin
+
+    f = eval(:(() -> begin
         pushPS($(varAddr))
         return NEXT
-    end)))
-    mem[mem[HERE]] = -length(primitives); mem[HERE] += 1
+    end))
 
+    mem[mem[HERE]] = defPrim(f, name=name); mem[HERE] += 1
     mem[mem[HERE]] = initial; mem[HERE] += 1
 
-    return varAddr
+    return varAddr, codeWordAddr
 end
 
 function defConst(name::AbstractString, val::Int64; flags::Int64=0)
-    defPrim(name, eval(:(() -> begin
+    defPrimWord(name, eval(:(() -> begin
         pushPS($(val))
         return NEXT
     end)))
@@ -155,35 +191,33 @@ function defConst(name::AbstractString, val::Int64; flags::Int64=0)
     return val
 end
 
-# Threading Primitives
+# Threading Primitives (inner interpreter)
 
-NEXT = defPrim("NEXT", () -> begin
+NEXT = defPrim(() -> begin
     reg.W = mem[reg.IP]
     reg.IP += 1
-    X = mem[reg.W]
-    return X
-end)
+    return mem[reg.W]
+end, name="NEXT")
 
-DOCOL = defPrim("DOCOL", () -> begin
+DOCOL = defPrim(() -> begin
     pushRS(reg.IP)
     reg.IP = reg.W + 1
     return NEXT
-end)
+end, name="DOCOL")
 
-EXIT = defPrim("EXIT", () -> begin
+EXIT = defPrimWord("EXIT", () -> begin
     reg.IP = popRS()
     return NEXT
 end)
 
-
 # Basic forth primitives
 
-DROP = defPrim("DROP", () -> begin
+DROP = defPrimWord("DROP", () -> begin
     popPS()
     return NEXT
 end)
 
-SWAP = defPrim("SWAP", () -> begin
+SWAP = defPrimWord("SWAP", () -> begin
     a = popPS()
     b = popPS()
     pushPS(a)
@@ -191,18 +225,18 @@ SWAP = defPrim("SWAP", () -> begin
     return NEXT
 end)
 
-DUP = defPrim("DUP", () -> begin
+DUP = defPrimWord("DUP", () -> begin
     pushPS(mem[reg.PSP])
     return NEXT
 end)
 
-OVER = defPrim("OVER", () -> begin
+OVER = defPrimWord("OVER", () -> begin
     ensurePSDepth(2)
     pushPS(mem[reg.PSP-1])
     return NEXT
 end)
 
-ROT = defPrim("ROT", () -> begin
+ROT = defPrimWord("ROT", () -> begin
     a = popPS()
     b = popPS()
     c = popPS()
@@ -212,7 +246,7 @@ ROT = defPrim("ROT", () -> begin
     return NEXT
 end)
 
-NROT = defPrim("-ROT", () -> begin
+NROT = defPrimWord("-ROT", () -> begin
     a = popPS()
     b = popPS()
     c = popPS()
@@ -222,13 +256,13 @@ NROT = defPrim("-ROT", () -> begin
     return NEXT
 end)
 
-TWODROP = defPrim("2DROP", () -> begin
+TWODROP = defPrimWord("2DROP", () -> begin
     popPS()
     popPS()
     return NEXT
 end)
 
-TWODUP = defPrim("2DUP", () -> begin
+TWODUP = defPrimWord("2DUP", () -> begin
     ensurePSDepth(2)
     a = mem[reg.PSP-1]
     b = mem[reg.PSP]
@@ -237,7 +271,7 @@ TWODUP = defPrim("2DUP", () -> begin
     return NEXT
 end)
 
-TWOSWAP = defPrim("2SWAP", () -> begin
+TWOSWAP = defPrimWord("2SWAP", () -> begin
     a = popPS()
     b = popPS()
     c = popPS()
@@ -249,7 +283,7 @@ TWOSWAP = defPrim("2SWAP", () -> begin
     return NEXT
 end)
 
-QDUP = defPrim("?DUP", () -> begin
+QDUP = defPrimWord("?DUP", () -> begin
     ensurePSDepth(1)
     val = mem[reg.PSP]
     if val != 0
@@ -258,7 +292,161 @@ QDUP = defPrim("?DUP", () -> begin
     return NEXT
 end)
 
-LIT = defPrim("LIT", () -> begin
+INCR = defPrimWord("1+", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] += 1
+    return NEXT
+end)
+
+DECR = defPrimWord("1-", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] -= 1
+    return NEXT
+end)
+
+INCR2 = defPrimWord("2+", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] += 2
+    return NEXT
+end)
+
+DECR2 = defPrimWord("2-", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] -= 2
+    return NEXT
+end)
+
+ADD = defPrimWord("+", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a+b)
+    return NEXT
+end)
+
+SUB = defPrimWord("-", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a-b)
+    return NEXT
+end)
+
+MUL = defPrimWord("*", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a*b)
+    return NEXT
+end)
+
+DIVMOD = defPrimWord("/MOD", () -> begin
+    b = popPS()
+    a = popPS()
+    q,r = divrem(a,b)
+    pushPS(r)
+    pushPS(q)
+    return NEXT
+end)
+
+EQU = defPrimWord("=", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a==b ? -1 : 0)
+    return NEXT
+end)
+
+NEQU = defPrimWord("<>", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a!=b ? -1 : 0)
+    return NEXT
+end)
+
+LT = defPrimWord("<", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a<b ? -1 : 0)
+    return NEXT
+end)
+
+GT = defPrimWord(">", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a>b ? -1 : 0)
+    return NEXT
+end)
+
+LE = defPrimWord("<=", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a<=b ? -1 : 0)
+    return NEXT
+end)
+
+GE = defPrimWord(">=", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a>=b ? -1 : 0)
+    return NEXT
+end)
+
+ZEQU = defPrimWord("0=", () -> begin
+    pushPS(popPS() == 0 ? -1 : 0)
+    return NEXT
+end)
+
+ZNEQU = defPrimWord("0<>", () -> begin
+    pushPS(popPS() != 0 ? -1 : 0)
+    return NEXT
+end)
+
+ZLT = defPrimWord("0<", () -> begin
+    pushPS(popPS() < 0 ? -1 : 0)
+    return NEXT
+end)
+
+ZGT = defPrimWord("0>", () -> begin
+    pushPS(popPS() > 0 ? -1 : 0)
+    return NEXT
+end)
+
+ZLE = defPrimWord("0<=", () -> begin
+    pushPS(popPS() <= 0 ? -1 : 0)
+    return NEXT
+end)
+
+ZGE = defPrimWord("0>=", () -> begin
+    pushPS(popPS() >= 0 ? -1 : 0)
+    return NEXT
+end)
+
+AND = defPrimWord("AND", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a & b)
+    return NEXT
+end)
+
+OR = defPrimWord("OR", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a | b)
+    return NEXT
+end)
+
+XOR = defPrimWord("XOR", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a $ b)
+    return NEXT
+end)
+
+INVERT = defPrimWord("INVERT", () -> begin
+    pushPS(~popPS())
+    return NEXT
+end)
+
+# Literals
+
+LIT = defPrimWord("LIT", () -> begin
     pushPS(mem[reg.IP])
     reg.IP += 1
     return NEXT
@@ -266,27 +454,27 @@ end)
 
 # Memory primitives
 
-STORE = defPrim("!", () -> begin
+STORE = defPrimWord("!", () -> begin
     addr = popPS()
     dat = popPS()
     mem[addr] = dat
     return NEXT
 end)
 
-FETCH = defPrim("@", () -> begin
+FETCH = defPrimWord("@", () -> begin
     addr = popPS()
     pushPS(mem[addr])
     return NEXT
 end)
 
-ADDSTORE = defPrim("+!", () -> begin
+ADDSTORE = defPrimWord("+!", () -> begin
     addr = popPS()
     toAdd = popPS()
     mem[addr] += toAdd
     return NEXT
 end)
 
-SUBSTORE = defPrim("-!", () -> begin
+SUBSTORE = defPrimWord("-!", () -> begin
     addr = popPS()
     toSub = popPS()
     mem[addr] -= toSub
@@ -296,72 +484,85 @@ end)
 
 # Built-in variables
 
-defExistingVar("HERE", HERE)
-defExistingVar("LATEST", LATEST)
-defExistingVar("PSP0", PSP0)
-defExistingVar("RSP0", RSP0)
-STATE = defNewVar("STATE", 0)
-BASE = defNewVar("BASE", 10)
+HERE_CFA = defExistingVar("HERE", HERE)
+LATEST_CFA = defExistingVar("LATEST", LATEST)
+PSP0_CFA = defExistingVar("PSP0", PSP0)
+RSP0_CFA = defExistingVar("RSP0", RSP0)
+STATE, STATE_CFA = defNewVar("STATE", 0)
+BASE, BASE_CFA = defNewVar("BASE", 10)
 
 # Constants
 
 defConst("VERSION", 1)
 defConst("DOCOL", DOCOL)
 defConst("DICT", DICT)
-F_IMMED = defConst("F_IMMED", 100)
-F_HIDEN = defConst("F_HIDDEN", 1000)
+F_IMMED = defConst("F_IMMED", 128)
+F_HIDDEN = defConst("F_HIDDEN", 256)
+F_LENMASK = defConst("F_LENMASK", 127)
 
 # Return Stack
 
-TOR = defPrim(">R", () -> begin
+TOR = defPrimWord(">R", () -> begin
     pushRS(popPS())
     return NEXT
 end)
 
-FROMR = defPrim("R>", () -> begin
+FROMR = defPrimWord("R>", () -> begin
     pushPS(popRS())
     return NEXT
 end)
 
-RSPFETCH = defPrim("RSP@", () -> begin
+RSPFETCH = defPrimWord("RSP@", () -> begin
     pushPS(reg.RSP)
     return NEXT
 end)
 
-RSPSTORE = defPrim("RSP!", () -> begin
+RSPSTORE = defPrimWord("RSP!", () -> begin
     RSP = popPS()
     return NEXT
 end)
 
-RDROP = defPrim("RDROP", () -> begin
+RDROP = defPrimWord("RDROP", () -> begin
     popRS()
     return NEXT
 end)
 
 # Parameter Stack
 
-PSPFETCH = defPrim("PSP@", () -> begin
+PSPFETCH = defPrimWord("PSP@", () -> begin
     pushPS(reg.PSP)
     return NEXT
 end)
 
-PSPSTORE = defPrim("PSP!", () -> begin
+PSPSTORE = defPrimWord("PSP!", () -> begin
     PSP = popPS()
     return NEXT
 end)
 
+# Working Register
+
+WFETCH = defPrimWord("W@", () -> begin
+    pushPS(reg.W)
+    return NEXT
+end)
+
+WSTORE = defPrimWord("W!", () -> begin
+    reg.W = popPS()
+    return NEXT
+end)
+
 # I/O
 
 defConst("TIB", TIB)
-NUMTIB = defNewVar("#TIB", 0)
-TOIN = defNewVar(">IN", 0)
+NUMTIB, NUMTIB_CFA = defNewVar("#TIB", 0)
+TOIN, TOIN_CFA = defNewVar(">IN", 0)
 
-KEY = defPrim("KEY", () -> begin
+KEY = defPrimWord("KEY", () -> begin
     if mem[TOIN] >= mem[NUMTIB]
         mem[TOIN] = 0
         line = readline()
         mem[NUMTIB] = length(line)
-        mem[TIB:(TIB+mem[NUMTIB]-1)] = [Int64(c) for c in collect(line)]
+        putString(line, TIB)
     end
 
     pushPS(mem[TIB + mem[TOIN]])
@@ -370,19 +571,19 @@ KEY = defPrim("KEY", () -> begin
     return NEXT
 end)
 
-EMIT = defPrim("EMIT", () -> begin
+EMIT = defPrimWord("EMIT", () -> begin
     print(Char(popPS()))
     return NEXT
 end)
 
-WORD = defPrim("WORD", () -> begin
+WORD = defPrimWord("WORD", () -> begin
     
     c = -1
 
     skip_to_end = false
     while true
 
-        callPrim(KEY)
+        callPrim(mem[KEY])
         c = Char(popPS())
 
         if c == '\\'
@@ -407,14 +608,25 @@ WORD = defPrim("WORD", () -> begin
     wordAddr = mem[HERE]
     offset = 0
 
+    if c == '\n'
+        # Treat newline as a special word
+
+        mem[wordAddr + offset] = Int64(c)
+        pushPS(wordAddr)
+        pushPS(1)
+        return NEXT
+    end
+
     while true
         mem[wordAddr + offset] = Int64(c)
         offset += 1
 
-        callPrim(KEY)
+        callPrim(mem[KEY])
         c = Char(popPS())
 
-        if c == ' ' || c == '\t'
+        if c == ' ' || c == '\t' || c == '\n'
+            # Rewind KEY
+            mem[TOIN] -= 1
             break
         end
     end
@@ -426,40 +638,306 @@ WORD = defPrim("WORD", () -> begin
 
     return NEXT
 end)
-#
-#NUMBER = defPrim("NUMBER", (reg) -> begin
-#
-#    return NEXT
-#end)
-#
-#### VM loop ####
-#function runVM(reg::Reg)
-#    jmp = NEXT
-#    while (jmp = callPrim(reg, jmp)) != 0 end
-#end
 
-# Debugging tools
+NUMBER = defPrimWord("NUMBER", () -> begin
 
-function coredump(startAddr::Int64; count::Int64 = 16, cellsPerLine::Int64 = 8)
-    chars = Array{Char,1}(cellsPerLine)
+    wordLen = popPS()
+    wordAddr = popPS()
+
+    s = getString(wordAddr, wordLen)
 
-    for i in 0:(count-1)
-        addr = startAddr + i
-        if i%cellsPerLine == 0
-            print("$addr:")
+    try
+        pushPS(parse(Int64, s, mem[BASE]))
+        pushPS(0)
+    catch
+        pushPS(1) # Error indication
+    end
+
+    return NEXT
+end)
+
+# Dictionary searches
+
+FIND = defPrimWord("FIND", () -> begin
+
+    wordLen = popPS()
+    wordAddr = popPS()
+    word = lowercase(getString(wordAddr, wordLen))
+
+    latest = LATEST
+    
+    i = 0
+    while (latest = mem[latest]) > 0
+        lenAndFlags = mem[latest+1]
+        len = lenAndFlags & F_LENMASK
+        hidden = (lenAndFlags & F_HIDDEN) == F_HIDDEN
+
+        if hidden || len != wordLen
+            continue
         end
+        
+        thisAddr = latest+2
+        thisWord = lowercase(getString(thisAddr, len))
 
-        print("\t$(mem[addr]) ")
+        if lowercase(thisWord) == lowercase(word)
+            break
+        end
+    end
+
+    pushPS(latest)
+
+    return NEXT
+end)
+
+TOCFA = defPrimWord(">CFA", () -> begin
+
+    addr = popPS()
+    lenAndFlags = mem[addr+1]
+    len = lenAndFlags & F_LENMASK
+
+    pushPS(addr + 2 + len)
+
+    return NEXT
+end)
+
+TODFA = defWord(">DFA", [TOCFA, INCR, EXIT])
+
+# Compilation
+
+CREATE = defPrimWord("CREATE", () -> begin
+
+    wordLen = popPS()
+    wordAddr = popPS()
+    word = getString(wordAddr, wordLen)
+
+    createHeader(word, 0)
+
+    return NEXT
+end)
+
+COMMA = defPrimWord(",", () -> begin
+    mem[mem[HERE]] = popPS()
+    mem[HERE] += 1
+
+    return NEXT
+end)
+
+LBRAC = defPrimWord("[", () -> begin
+    mem[STATE] = 0
+    return NEXT
+end, flags=F_IMMED)
+
+RBRAC = defPrimWord("]", () -> begin
+    mem[STATE] = 1
+    return NEXT
+end, flags=F_IMMED)
+
+HIDDEN = defPrimWord("HIDDEN", () -> begin
+    addr = popPS() + 1
+    mem[addr] = mem[addr] $ F_HIDDEN
+    return NEXT
+end)
+
+HIDE = defWord("HIDE",
+    [WORD,
+    FIND,
+    HIDDEN,
+    EXIT])
+
+COLON = defWord(":",
+    [WORD,
+    CREATE,
+    LIT, DOCOL, COMMA,
+    LATEST_CFA, FETCH, HIDDEN,
+    RBRAC,
+    EXIT])
+
+SEMICOLON = defWord(";",
+    [LIT, EXIT, COMMA,
+    LATEST_CFA, FETCH, HIDDEN,
+    LBRAC,
+    EXIT], flags=F_IMMED)
+
+IMMEDIATE = defPrimWord("IMMEDIATE", () -> begin
+    lenAndFlagsAddr = mem[LATEST] + 1
+    mem[lenAndFlagsAddr] = mem[lenAndFlagsAddr] $ F_IMMED
+    return NEXT
+end, flags=F_IMMED)
+
+TICK = defWord("'", [WORD, FIND, TOCFA, EXIT])
+
+# Branching
+
+BRANCH = defPrimWord("BRANCH", () -> begin
+    reg.IP += mem[reg.IP]
+    return NEXT
+end)
+
+ZBRANCH = defPrimWord("0BRANCH", () -> begin
+    if (popPS() == 0)
+        reg.IP += mem[reg.IP]
+    else
+        reg.IP += 1
+    end
 
-        if (mem[addr]>=32 && mem[addr]<176)
-            chars[i%cellsPerLine + 1] = Char(mem[addr])
+    return NEXT
+end)
+
+# Strings
+
+LITSTRING = defPrimWord("LITSTRING", () -> begin
+    len = mem[reg.IP]
+    reg.IP += 1
+    pushPS(reg.IP)
+    pushPS(len)
+    reg.IP += len
+
+    return NEXT
+end)
+
+TELL = defPrimWord("TELL", () -> begin
+    len = popPS()
+    addr = popPS()
+    str = getString(addr, len)
+    print(str)
+    return NEXT
+end)
+
+# Outer interpreter
+
+EXECUTE = defPrimWord("EXECUTE", () -> begin
+    reg.W = popPS()
+    return mem[reg.W]
+end)
+
+INTERPRET = defPrimWord("INTERPRET", () -> begin
+
+    callPrim(mem[WORD])
+
+    wordName = getString(mem[reg.PSP-1], mem[reg.PSP])
+    #println("... ", replace(wordName, "\n", "\\n"), " ...")
+
+    callPrim(mem[TWODUP])
+    callPrim(mem[FIND])
+
+    wordAddr = mem[reg.PSP]
+
+    if wordAddr>0
+        # Word in dictionary
+
+        isImmediate = (mem[wordAddr+1] & F_IMMED) != 0
+        callPrim(mem[TOCFA])
+
+        callPrim(mem[ROT]) # get rid of extra copy of word string details
+        popPS()
+        popPS()
+
+        if mem[STATE] == 0 || isImmediate
+            # Execute!
+            #println("Executing CFA at $(mem[reg.PSP])")
+            return callPrim(mem[EXECUTE])
         else
-            chars[i%cellsPerLine + 1] = '.'
+            # Append CFA to dictionary
+            callPrim(mem[COMMA])
         end
+    else
+        # Not in dictionary, assume number
+
+        popPS()
+
+        callPrim(mem[NUMBER])
+
+        if popPS() != 0
+            println("Parse error at word: '$wordName'")
+            return NEXT
+        end
+
+        if mem[STATE] == 0
+            # Number already on stack!
+        else
+            # Append literal to dictionary
+            pushPS(LIT)
+            callPrim(mem[COMMA])
+            callPrim(mem[COMMA])
+        end
+    end
+
+    return NEXT
+end)
+
+QUIT = defWord("QUIT",
+    [RSP0_CFA, RSPSTORE,
+    INTERPRET,
+    BRANCH,-2])
+
+NL = defPrimWord("\n", () -> begin
+    if mem[STATE] == 0
+        println(" ok")
+    end
+    return NEXT
+end, flags=F_IMMED)
+
+# Odds and Ends
+
+CHAR = defPrimWord("CHAR", () -> begin
+    callPrim(mem[WORD])
+    wordLen = popPS()
+    wordAddr = popPS()
+    word = getString(wordAddr, wordLen)
+    pushPS(Int64(word[1]))
+
+    return NEXT
+end)
+
+BYE = defPrimWord("BYE", () -> begin
+    return 0
+end)
+
+#### VM loop ####
+function runVM()
+    # Start with IP pointing to first instruction of outer interpreter
+    reg.IP = QUIT + 1
+
+    # Primitive processing loop.
+    # Everyting else is simply a consequence of this loop!
+    jmp = NEXT
+    while (jmp = callPrim(jmp)) != 0
+        #println("Evaluating prim $jmp [$(primNames[-jmp])]")
+    end
+end
 
-        if i%cellsPerLine == cellsPerLine-1
-            println(string("\t", ASCIIString(chars)))
+# Debugging tools
+
+function dump(startAddr::Int64; count::Int64 = 100, cellsPerLine::Int64 = 10)
+    chars = Array{Char,1}(cellsPerLine)
+
+    lineStartAddr = cellsPerLine*div((startAddr-1),cellsPerLine) + 1
+    endAddr = startAddr + count - 1
+
+    q, r = divrem((endAddr-lineStartAddr+1), cellsPerLine)
+    numLines = q + (r > 0 ? 1 : 0)
+
+    i = lineStartAddr
+    for l in 1:numLines
+        print(i,":")
+
+        for c in 1:cellsPerLine
+            if i >= startAddr && i <= endAddr
+                print("\t",mem[i])
+                if mem[i]>=32 && mem[i]<128
+                    chars[c] = Char(mem[i])
+                else
+                    chars[c] = '.'
+                end
+            else
+                print("\t")
+                chars[c] = ' '
+            end
+
+            i += 1
         end
+
+        println("\t", ASCIIString(chars))
     end
 end
 
@@ -477,4 +955,18 @@ function printPS()
     end
 end
 
+function printRS()
+    count = reg.RSP - mem[RSP0]
+
+    if count > 0
+        print("<$count>")
+        for i in (mem[RSP0]+1):reg.RSP
+            print(" $(mem[i])")
+        end
+        println()
+    else
+        println("Return stack empty")
+    end
+end
+
 end