X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=src%2Fforth.jl;h=3363ea7bdd330fd26e945fa4d302a05dfeb0ec89;hb=29f8abf4f2166ec79d2250dae952d08021224631;hp=67dd77db1bacdf764753a14e59d9042f30b641ff;hpb=bc72871b5a63fc748a71d55d87afca3746d8d219;p=forth.jl.git

diff --git a/src/forth.jl b/src/forth.jl
index 67dd77d..3363ea7 100644
--- a/src/forth.jl
+++ b/src/forth.jl
@@ -1,47 +1,941 @@
 module forth
 
-RS = Array{Int, 1}()
-DS = Array{Int, 1}()
-
-IP = 0
-W = 0
-X = 0
-jmp = nothing
-
-primitives = Array{Expr,1}()
-memory = Array{Int64,1}()
-headers = Array{Tuple{AbstractString, Int64},1}()
-
-function addPrim(name::AbstractString, expr::Expr)
-    push!(primitives, expr)
-    push!(memory, -length(primitives))
-    push!(headers, (name, length(memory)))
+# VM mem size
+size_mem = 640*1024
+
+# Buffer sizes
+size_RS = 1024   # Return stack size
+size_PS = 1024   # Parameter stack size
+size_TIB = 1096  # Terminal input buffer size
+
+# The mem array constitutes the memory of the VM. It has the following geography:
+#
+# mem = +-----------------------+
+#       | Built-in Variables    |
+#       +-----------------------+
+#       | Return Stack          |
+#       +-----------------------+
+#       | Parameter Stack       |
+#       +-----------------------+
+#       | Terminal Input Buffer |
+#       +-----------------------+
+#       | Dictionary            |
+#       +-----------------------+
+#
+# Note that all words (user-defined, primitive, variables, etc) are included in
+# the dictionary.
+#
+# Simple linear addressing is used with one exception: references to primitive code
+# blocks, which are represented as anonymous functions, appear the negative index
+# into the primitives array which contains only these functions.
+
+mem = Array{Int64,1}(size_mem)
+primitives = Array{Function,1}()
+
+# Built-in variables
+
+nextVarAddr = 1
+RSP0 = nextVarAddr; nextVarAddr += 1
+PSP0 = nextVarAddr; nextVarAddr += 1
+HERE = nextVarAddr; nextVarAddr += 1
+LATEST = nextVarAddr; nextVarAddr += 1
+
+mem[RSP0] = nextVarAddr              # bottom of RS
+mem[PSP0] = mem[RSP0] + size_RS      # bottom of PS
+TIB = mem[PSP0] + size_PS            # address of terminal input buffer
+mem[HERE] = TIB + size_TIB           # location of bottom of dictionary
+mem[LATEST] = 0                      # no previous definition
+
+DICT = mem[HERE] # Save bottom of dictionary as constant
+
+# VM registers
+type Reg
+    RSP::Int64  # Return stack pointer
+    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)
+
+# Stack manipulation
+
+type StackUnderflow <: Exception end
+
+getRSDepth() = reg.RSP - mem[RSP0]
+getPSDepth() = reg.PSP - mem[PSP0]
+
+function ensurePSDepth(depth::Int64)
+    if getPSDepth()<depth
+        throw(StackUnderflow())
+    end
+end
+
+function ensureRSDepth(depth::Int64)
+    if getRSDepth()<depth
+        throw(StackUnderflow())
+    end
+end
+
+function pushRS(val::Int64)
+    mem[reg.RSP+=1] = val
+end
+
+function popRS()
+    ensureRSDepth(1)
+
+    val = mem[reg.RSP]
+    reg.RSP -= 1
+    return val
+end
+
+function pushPS(val::Int64)
+    mem[reg.PSP += 1] = val
+end
+
+function popPS()
+    ensurePSDepth(1)
+
+    val = mem[reg.PSP]
+    reg.PSP -= 1
+    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 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
+    putString(name, mem[HERE]); mem[HERE] += length(name)
+end
+
+function defPrim(name::AbstractString, f::Function; flags::Int64=0)
+    createHeader(name, flags)
+
+    codeWordAddr = mem[HERE]
+    push!(primitives, f)
+    mem[codeWordAddr] = -length(primitives)
+    mem[HERE] += 1
+
+    return codeWordAddr
+end
+
+callPrim(addr::Int64) = primitives[-addr]()
+
+function defExistingVar(name::AbstractString, varAddr::Int64; flags::Int64=0)
+    defPrim(name, eval(:(() -> begin
+        pushPS($(varAddr))
+        return mem[NEXT]
+    end)))
+end
+
+function defNewVar(name::AbstractString, initial::Int64; flags::Int64=0)
+    createHeader(name, flags)
+    
+    codeWordAddr = mem[HERE]
+    varAddr = mem[HERE] + 1
+    push!(primitives, eval(:(() -> begin
+        pushPS($(varAddr))
+        return mem[NEXT]
+    end)))
+    mem[mem[HERE]] = -length(primitives); mem[HERE] += 1
+
+    mem[mem[HERE]] = initial; mem[HERE] += 1
+
+    return varAddr, codeWordAddr
+end
+
+function defConst(name::AbstractString, val::Int64; flags::Int64=0)
+    defPrim(name, eval(:(() -> begin
+        pushPS($(val))
+        return mem[NEXT]
+    end)))
+
+    return val
+end
+
+function defWord(name::AbstractString, wordAddrs::Array{Int64,1}; flags::Int64=0)
+    createHeader(name, flags)
+
+    addr = mem[HERE]
+    mem[mem[HERE]] = mem[DOCOL]
+    mem[HERE] += 1
+
+    for wordAddr in wordAddrs
+        mem[mem[HERE]] = wordAddr
+        mem[HERE] += 1
+    end
+
+    return addr
+end
+
+# Threading Primitives (inner interpreter)
+
+NEXT = defPrim("NEXT", () -> begin
+    reg.W = mem[reg.IP]
+    reg.IP += 1
+    return mem[reg.W]
+end)
+
+DOCOL = defPrim("DOCOL", () -> begin
+    pushRS(reg.IP)
+    reg.IP = reg.W + 1
+    return mem[NEXT]
+end)
+
+EXIT = defPrim("EXIT", () -> begin
+    reg.IP = popRS()
+    return mem[NEXT]
+end)
+
+# Basic forth primitives
+
+DROP = defPrim("DROP", () -> begin
+    popPS()
+    return mem[NEXT]
+end)
+
+SWAP = defPrim("SWAP", () -> begin
+    a = popPS()
+    b = popPS()
+    pushPS(a)
+    pushPS(b)
+    return mem[NEXT]
+end)
+
+DUP = defPrim("DUP", () -> begin
+    pushPS(mem[reg.PSP])
+    return mem[NEXT]
+end)
+
+OVER = defPrim("OVER", () -> begin
+    ensurePSDepth(2)
+    pushPS(mem[reg.PSP-1])
+    return mem[NEXT]
+end)
+
+ROT = defPrim("ROT", () -> begin
+    a = popPS()
+    b = popPS()
+    c = popPS()
+    pushPS(a)
+    pushPS(c)
+    pushPS(b)
+    return mem[NEXT]
+end)
+
+NROT = defPrim("-ROT", () -> begin
+    a = popPS()
+    b = popPS()
+    c = popPS()
+    pushPS(b)
+    pushPS(a)
+    pushPS(c)
+    return mem[NEXT]
+end)
+
+TWODROP = defPrim("2DROP", () -> begin
+    popPS()
+    popPS()
+    return mem[NEXT]
+end)
+
+TWODUP = defPrim("2DUP", () -> begin
+    ensurePSDepth(2)
+    a = mem[reg.PSP-1]
+    b = mem[reg.PSP]
+    pushPS(a)
+    pushPS(b)
+    return mem[NEXT]
+end)
+
+TWOSWAP = defPrim("2SWAP", () -> begin
+    a = popPS()
+    b = popPS()
+    c = popPS()
+    d = popPS()
+    pushPS(b)
+    pushPS(a)
+    pushPS(c)
+    pushPS(d)
+    return mem[NEXT]
+end)
+
+QDUP = defPrim("?DUP", () -> begin
+    ensurePSDepth(1)
+    val = mem[reg.PSP]
+    if val != 0
+        pushPS(val)
+    end
+    return mem[NEXT]
+end)
+
+INCR = defPrim("1+", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] += 1
+    return mem[NEXT]
+end)
+
+DECR = defPrim("1-", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] -= 1
+    return mem[NEXT]
+end)
+
+INCR2 = defPrim("2+", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] += 2
+    return mem[NEXT]
+end)
+
+DECR2 = defPrim("2-", () -> begin
+    ensurePSDepth(1)
+    mem[reg.PSP] -= 2
+    return mem[NEXT]
+end)
+
+ADD = defPrim("+", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a+b)
+    return mem[NEXT]
+end)
+
+SUB = defPrim("-", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a-b)
+    return mem[NEXT]
+end)
+
+MUL = defPrim("*", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a*b)
+    return mem[NEXT]
+end)
+
+DIVMOD = defPrim("/MOD", () -> begin
+    b = popPS()
+    a = popPS()
+    q,r = divrem(a,b)
+    pushPS(r)
+    pushPS(q)
+    return mem[NEXT]
+end)
+
+EQU = defPrim("=", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a==b ? -1 : 0)
+    return mem[NEXT]
+end)
+
+NEQU = defPrim("<>", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a!=b ? -1 : 0)
+    return mem[NEXT]
+end)
+
+LT = defPrim("<", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a<b ? -1 : 0)
+    return mem[NEXT]
+end)
+
+GT = defPrim(">", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a>b ? -1 : 0)
+    return mem[NEXT]
+end)
+
+LE = defPrim("<=", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a<=b ? -1 : 0)
+    return mem[NEXT]
+end)
+
+GE = defPrim(">=", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a>=b ? -1 : 0)
+    return mem[NEXT]
+end)
+
+ZEQU = defPrim("0=", () -> begin
+    pushPS(popPS() == 0 ? -1 : 0)
+    return mem[NEXT]
+end)
+
+ZNEQU = defPrim("0<>", () -> begin
+    pushPS(popPS() != 0 ? -1 : 0)
+    return mem[NEXT]
+end)
+
+ZLT = defPrim("0<", () -> begin
+    pushPS(popPS() < 0 ? -1 : 0)
+    return mem[NEXT]
+end)
+
+ZGT = defPrim("0>", () -> begin
+    pushPS(popPS() > 0 ? -1 : 0)
+    return mem[NEXT]
+end)
+
+ZLE = defPrim("0<=", () -> begin
+    pushPS(popPS() <= 0 ? -1 : 0)
+    return mem[NEXT]
+end)
+
+ZGE = defPrim("0>=", () -> begin
+    pushPS(popPS() >= 0 ? -1 : 0)
+    return mem[NEXT]
+end)
+
+AND = defPrim("AND", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a & b)
+    return mem[NEXT]
+end)
+
+OR = defPrim("OR", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a | b)
+    return mem[NEXT]
+end)
+
+XOR = defPrim("XOR", () -> begin
+    b = popPS()
+    a = popPS()
+    pushPS(a $ b)
+    return mem[NEXT]
+end)
+
+INVERT = defPrim("INVERT", () -> begin
+    pushPS(~popPS())
+    return mem[NEXT]
+end)
+
+# Literals
+
+LIT = defPrim("LIT", () -> begin
+    pushPS(mem[reg.IP])
+    reg.IP += 1
+    return mem[NEXT]
+end)
+
+# Memory primitives
+
+STORE = defPrim("!", () -> begin
+    addr = popPS()
+    dat = popPS()
+    mem[addr] = dat
+    return mem[NEXT]
+end)
+
+FETCH = defPrim("@", () -> begin
+    addr = popPS()
+    pushPS(mem[addr])
+    return mem[NEXT]
+end)
+
+ADDSTORE = defPrim("+!", () -> begin
+    addr = popPS()
+    toAdd = popPS()
+    mem[addr] += toAdd
+    return mem[NEXT]
+end)
+
+SUBSTORE = defPrim("-!", () -> begin
+    addr = popPS()
+    toSub = popPS()
+    mem[addr] -= toSub
+    return mem[NEXT]
+end)
+
+
+# Built-in variables
+
+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", 128)
+F_HIDDEN = defConst("F_HIDDEN", 256)
+F_LENMASK = defConst("F_LENMASK", 127)
+
+# Return Stack
+
+TOR = defPrim(">R", () -> begin
+    pushRS(popPS())
+    return mem[NEXT]
+end)
+
+FROMR = defPrim("R>", () -> begin
+    pushPS(popRS())
+    return mem[NEXT]
+end)
+
+RSPFETCH = defPrim("RSP@", () -> begin
+    pushPS(reg.RSP)
+    return mem[NEXT]
+end)
+
+RSPSTORE = defPrim("RSP!", () -> begin
+    RSP = popPS()
+    return mem[NEXT]
+end)
+
+RDROP = defPrim("RDROP", () -> begin
+    popRS()
+    return mem[NEXT]
+end)
+
+# Parameter Stack
+
+PSPFETCH = defPrim("PSP@", () -> begin
+    pushPS(reg.PSP)
+    return mem[NEXT]
+end)
+
+PSPSTORE = defPrim("PSP!", () -> begin
+    PSP = popPS()
+    return mem[NEXT]
+end)
+
+# I/O
+
+defConst("TIB", TIB)
+NUMTIB, NUMTIB_CFA = defNewVar("#TIB", 0)
+TOIN, TOIN_CFA = defNewVar(">IN", 0)
+
+KEY = defPrim("KEY", () -> begin
+    if mem[TOIN] >= mem[NUMTIB]
+        mem[TOIN] = 0
+        line = readline()
+        mem[NUMTIB] = length(line)
+        putString(line, TIB)
+    end
+
+    pushPS(mem[TIB + mem[TOIN]])
+    mem[TOIN] += 1
+
+    return mem[NEXT]
+end)
+
+EMIT = defPrim("EMIT", () -> begin
+    print(Char(popPS()))
+    return mem[NEXT]
+end)
+
+WORD = defPrim("WORD", () -> begin
+    
+    c = -1
+
+    skip_to_end = false
+    while true
+
+        callPrim(mem[KEY])
+        c = Char(popPS())
+
+        if c == '\\'
+            skip_to_end = true
+            continue
+        end
+
+        if skip_to_end
+            if c == '\n'
+                skip_to_end = false
+            end
+            continue
+        end
+
+        if c == ' ' || c == '\t'
+            continue
+        end
+
+        break
+    end
+
+    wordAddr = mem[HERE]
+    offset = 0
+
+    if c == '\n'
+        # Treat newline as a special word
+
+        mem[wordAddr + offset] = Int64(c)
+        pushPS(wordAddr)
+        pushPS(1)
+        return mem[NEXT]
+    end
+
+    while true
+        mem[wordAddr + offset] = Int64(c)
+        offset += 1
+
+        callPrim(mem[KEY])
+        c = Char(popPS())
+
+        if c == ' ' || c == '\t' || c == '\n'
+            # Rewind KEY
+            mem[TOIN] -= 1
+            break
+        end
+    end
+
+    wordLen = offset
+
+    pushPS(wordAddr)
+    pushPS(wordLen)
+
+    return mem[NEXT]
+end)
+
+NUMBER = defPrim("NUMBER", () -> begin
+
+    wordLen = popPS()
+    wordAddr = popPS()
+
+    s = getString(wordAddr, wordLen)
+
+    try
+        pushPS(parse(Int64, s, mem[BASE]))
+        pushPS(0)
+    catch
+        pushPS(1) # Error indication
+    end
+
+    return mem[NEXT]
+end)
+
+# Dictionary searches
+
+FIND = defPrim("FIND", () -> begin
+
+    wordLen = popPS()
+    wordAddr = popPS()
+    word = lowercase(getString(wordAddr, wordLen))
+
+    latest = LATEST
     
-    return expr
-end
-
-NEXT = addPrim("next", :(begin
-    W = memory[IP]
-    IP += 1
-    X = memory[W]
-    jmp = primitives[-X]
-end))
-
-DOCOL = addPrim("docol", :(begin
-    push!(RS, IP)
-    IP = W + 1
-    jmp = NEXT
-end))
-
-EXIT = addPrim("exit", :(begin
-    IP = pop!(RS)
-    jmp = NEXT
-end))
-
-# VM loop
-#jmp = NEXT
-#while true
-#    eval(jmp)
-#end
+    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))
+
+        if lowercase(thisWord) == lowercase(word)
+            break
+        end
+    end
+
+    pushPS(latest)
+
+    return mem[NEXT]
+end)
+
+TOCFA = defPrim(">CFA", () -> begin
+
+    addr = popPS()
+    lenAndFlags = mem[addr+1]
+    len = lenAndFlags & F_LENMASK
+
+    pushPS(addr + 2 + len)
+
+    return mem[NEXT]
+end)
+
+TODFA = defWord(">DFA", [TOCFA, INCR, EXIT])
+
+# Compilation
+
+CREATE = defPrim("CREATE", () -> begin
+
+    wordLen = popPS()
+    wordAddr = popPS()
+    word = getString(wordAddr, wordLen)
+
+    createHeader(word, 0)
+
+    return mem[NEXT]
+end)
+
+COMMA = defPrim(",", () -> begin
+    mem[mem[HERE]] = popPS()
+    mem[HERE] += 1
+
+    return mem[NEXT]
+end)
+
+LBRAC = defPrim("[", () -> begin
+    mem[STATE] = 0
+    return mem[NEXT]
+end, flags=F_IMMED)
+
+RBRAC = defPrim("]", () -> begin
+    mem[STATE] = 1
+    return mem[NEXT]
+end, flags=F_IMMED)
+
+HIDDEN = defPrim("HIDDEN", () -> begin
+    addr = popPS() + 1
+    mem[addr] = mem[addr] $ F_HIDDEN
+    return mem[NEXT]
+end)
+
+HIDE = defWord("HIDE",
+    [WORD,
+    FIND,
+    HIDDEN,
+    EXIT])
+
+COLON = defWord(":",
+    [WORD,
+    CREATE,
+    LIT, DOCOL, COMMA,
+    LATEST, FETCH, HIDDEN,
+    RBRAC,
+    EXIT])
+
+SEMICOLON = defWord(";",
+    [LIT, EXIT, COMMA,
+    LATEST, FETCH, HIDDEN,
+    LBRAC,
+    EXIT], flags=F_IMMED)
+
+IMMEDIATE = defPrim("IMMEDIATE", () -> begin
+    lenAndFlagsAddr = mem[LATEST] + 1
+    mem[lenAndFlagsAddr] = mem[lenAndFlagsAddr] $ F_IMMED
+    return mem[NEXT]
+end, flags=F_IMMED)
+
+TICK = defWord("'", [WORD, FIND, TOCFA, EXIT])
+
+# Branching
+
+BRANCH = defPrim("BRANCH", () -> begin
+    reg.IP += mem[reg.IP]
+    return mem[NEXT]
+end)
+
+ZBRANCH = defPrim("0BRANCH", () -> begin
+    if (popPS() == 0)
+        reg.IP += mem[reg.IP]
+    else
+        reg.IP += 1
+    end
+
+    return mem[NEXT]
+end)
+
+# Strings
+
+LITSTRING = defPrim("LITSTRING", () -> begin
+    len = mem[reg.IP]
+    reg.IP += 1
+    pushPS(reg.IP)
+    pushPS(len)
+    reg.IP += len
+
+    return mem[NEXT]
+end)
+
+TELL = defPrim("TELL", () -> begin
+    len = popPS()
+    addr = popPS()
+    str = getString(addr, len)
+    print(str)
+    return mem[NEXT]
+end)
+
+# Outer interpreter
+
+INTERPRET = defPrim("INTERPRET", () -> begin
+
+    callPrim(mem[WORD])
+    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!
+            return mem[popPS()]
+        else
+            # Append CFA to dictionary
+            callPrim(mem[COMMA])
+        end
+    else
+        # Not in dictionary, assume number
+
+        popPS()
+
+        wordName = getString(mem[reg.PSP-1], mem[reg.PSP])
+
+        callPrim(mem[NUMBER])
+
+        if popPS() != 0
+            println("Parse error at word: '$wordName'")
+            return mem[NEXT]
+        else
+        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 mem[NEXT]
+end)
+
+QUIT = defWord("QUIT",
+    [RSP0_CFA, RSPSTORE,
+    INTERPRET,
+    BRANCH,-2])
+
+NL = defPrim("\n", () -> begin
+    println(" ok")
+    return mem[NEXT]
+end)
+
+# Odds and Ends
+
+CHAR = defPrim("CHAR", () -> begin
+    callPrim(mem[WORD])
+    wordLen = popPS()
+    wordAddr = popPS()
+    word = getString(wordAddr, wordLen)
+    pushPS(Int64(word[1]))
+
+    return mem[NEXT]
+end)
+
+EXECUTE = defPrim("EXECUTE", () -> begin
+    return mem[popPS()]
+end)
+
+BYE = defPrim("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 = mem[NEXT]
+    while (jmp = callPrim(jmp)) != 0 end
+end
+
+# 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
+
+function printPS()
+    count = reg.PSP - mem[PSP0]
+
+    if count > 0
+        print("<$count>")
+        for i in (mem[PSP0]+1):reg.PSP
+            print(" $(mem[i])")
+        end
+        println()
+    else
+        println("Parameter stack empty")
+    end
+end
+
+function printRS()
+    count = reg.RSP - mem[RSP0]
+
+    if count > 0
+        print("<$count>")
+        for i in (mem[RSP0]+1):reg.RSP
+            print(" $(mem[i])")
+        end
+        println()
+    else
+        println("Return stack empty")
+    end
+end
 
 end