X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=src%2Fforth.jl;h=4f0cb1c57946e501bc392724d4589e0489174c5c;hb=dc7e7f71c57e84f1171ae24db8a80bec731ce2b4;hp=5bcd58311a0cfe8b28ebfdac9a22472f3d97c1c5;hpb=8c73ef04c814fa41e6d4dd72ec7c599dc065b7eb;p=forth.jl.git

diff --git a/src/forth.jl b/src/forth.jl
index 5bcd583..4f0cb1c 100644
--- a/src/forth.jl
+++ b/src/forth.jl
@@ -1,36 +1,26 @@
 module forth
 
-# VM memory size
-size_memory = 640*1024
+# VM mem size
+size_mem = 640*1024
 
 # Buffer sizes
-size_RS = 1024  # Return stack size
-size_PS = 1024  # Parameter stack size
-size_TIB = 4096 # Terminal input buffer size
+size_RS = 1024   # Return stack size
+size_PS = 1024   # Parameter stack size
+size_TIB = 1096  # Terminal input buffer size
 
-# VM registers
-RSP = 0 # Return stack pointer
-PSP =0  # Parameter/data stack pointer
-IP = 0  # Instruction pointer
-W = 0   # Working register
-X = 0   # Extra register
-
-RSP0 = 1
-PSP0 = RSP0 + size_RS
-here = PSP0 + size_PS + size_TIB  # location of bottom of dictionary
-latest = 0 # no previous definition
-
-# The following array constitutes the memory of the VM. It has the following geography:
+# The mem array constitutes the memory of the VM. It has the following geography:
 #
-# memory = +-----------------------+
-#          | Return Stack          |
-#          +-----------------------+
-#          | Parameter Stack       |
-#          +-----------------------+
-#          | Terminal Input Buffer |
-#          +-----------------------+
-#          | Dictionary            |
-#          +-----------------------+
+# 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.
@@ -39,233 +29,793 @@ latest = 0 # no previous definition
 # blocks, which are represented as anonymous functions, appear the negative index
 # into the primitives array which contains only these functions.
 
-memory = Array{Int64,1}(size_memory)
+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]
 
-# Stack manipulation functions
+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)
-    global RSP
-    memory[RSP+=1] = val
+    mem[reg.RSP+=1] = val
 end
 
 function popRS()
-    global RSP
-    val = memory[RSP]
-    RSP -= 1
+    ensureRSDepth(1)
+
+    val = mem[reg.RSP]
+    reg.RSP -= 1
     return val
 end
 
 function pushPS(val::Int64)
-    global PSP
-    memory[PSP += 1] = val
+    mem[reg.PSP += 1] = val
 end
 
 function popPS()
-    global PSP
-    val = PS[PSP]
-    PSP -= 1
+    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 defPrim(name::AbstractString, f::Function)
-    global latest, here
+function createHeader(name::AbstractString, flags::Int64)
+    mem[mem[HERE]] = mem[LATEST]
+    mem[LATEST] = mem[HERE]
+    mem[HERE] += 1
 
-    memory[here] = latest
-    latest = here
-    here += 1
+    mem[mem[HERE]] = length(name) | flags; mem[HERE] += 1
+    putString(name, mem[HERE]); mem[HERE] += length(name)
+end
 
-    memory[here] = length(name); here += 1
-    memory[here:(here+length(name)-1)] = [Int(c) for c in name]; here += length(name)
+function defPrim(name::AbstractString, f::Function; flags::Int64=0)
+    createHeader(name, flags)
 
+    codeWordAddr = mem[HERE]
     push!(primitives, f)
-    memory[here] = -length(primitives)
-    here += 1
+    mem[codeWordAddr] = -length(primitives)
+    mem[HERE] += 1
 
-    return -length(primitives)
+    return codeWordAddr
 end
 
 callPrim(addr::Int64) = primitives[-addr]()
 
-function defVar(name::AbstractString, val::Int64)
-    global latest, here
+function defExistingVar(name::AbstractString, varAddr::Int64; flags::Int64=0)
+    defPrim(name, eval(:(() -> begin
+        pushPS($(varAddr))
+        return mem[NEXT]
+    end)))
+end
 
-    memory[here] = latest
-    latest = here
-    here += 1
+function defNewVar(name::AbstractString, initial::Int64; flags::Int64=0)
+    createHeader(name, flags)
+    
+    varAddr = mem[HERE] + 1
+    push!(primitives, eval(:(() -> begin
+        pushPS($(varAddr))
+        return mem[NEXT]
+    end)))
+    mem[mem[HERE]] = -length(primitives); mem[HERE] += 1
 
-    memory[here] = length(name); here += 1
-    memory[here:(here+length(name)-1)] = [Int(c) for c in name]; here += length(name)
+    mem[mem[HERE]] = initial; mem[HERE] += 1
 
-    push!(primitives, () -> begin
+    return varAddr
+end
 
-    end)
+function defConst(name::AbstractString, val::Int64; flags::Int64=0)
+    defPrim(name, eval(:(() -> begin
+        pushPS($(val))
+        return mem[NEXT]
+    end)))
 
-    pushPS($var)
-    jmp = NEXT
+    return val
 end
 
-# Threading Primitives
+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
-    W = memory[IP]
-    IP += 1
-    X = memory[W]
-    return X
+    reg.W = mem[reg.IP]
+    reg.IP += 1
+    return mem[reg.W]
 end)
 
 DOCOL = defPrim("DOCOL", () -> begin
-    pushRS(IP)
-    IP = W + 1
-    return NEXT
+    pushRS(reg.IP)
+    reg.IP = reg.W + 1
+    return mem[NEXT]
 end)
 
 EXIT = defPrim("EXIT", () -> begin
-    IP = popRS()
-    return NEXT
+    reg.IP = popRS()
+    return mem[NEXT]
 end)
 
-
 # Basic forth primitives
 
 DROP = defPrim("DROP", () -> begin
     popPS()
-    return NEXT
+    return mem[NEXT]
 end)
 
 SWAP = defPrim("SWAP", () -> begin
-    PS[PSP], PS[PSP-1] = PS[PSP-1], PS[PS]
-    return NEXT
+    a = popPS()
+    b = popPS()
+    pushPS(a)
+    pushPS(b)
+    return mem[NEXT]
 end)
 
 DUP = defPrim("DUP", () -> begin
-    pushPS(PS[PSP])
-    return NEXT
+    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(memory[IP])
-    IP += 1
-    return NEXT
+    pushPS(mem[reg.IP])
+    reg.IP += 1
+    return mem[NEXT]
 end)
 
 # Memory primitives
 
-STORE = defPrim("!", quote
+STORE = defPrim("!", () -> begin
     addr = popPS()
     dat = popPS()
-    memory[addr] = dat
-    return NEXT
+    mem[addr] = dat
+    return mem[NEXT]
 end)
 
-FETCH = defPrim("@", quote
+FETCH = defPrim("@", () -> begin
     addr = popPS()
-    pushPS(memory[addr])
-    return NEXT
+    pushPS(mem[addr])
+    return mem[NEXT]
 end)
 
-ADDSTORE = defPrim("+!", quote
+ADDSTORE = defPrim("+!", () -> begin
     addr = popPS()
     toAdd = popPS()
-    memory[addr] += toAdd
-    return NEXT
+    mem[addr] += toAdd
+    return mem[NEXT]
 end)
 
-SUBSTORE = defPrim("-!", quote
+SUBSTORE = defPrim("-!", () -> begin
     addr = popPS()
     toSub = popPS()
-    memory[addr] -= toSub
-    return NEXT
+    mem[addr] -= toSub
+    return mem[NEXT]
 end)
 
 
 # Built-in variables
 
-defVar("STATE", :state)
-defVar("HERE", :here)
-defVar("LATEST", :latest)
-defVar("BASE", :base)
+defExistingVar("HERE", HERE)
+defExistingVar("LATEST", LATEST)
+defExistingVar("PSP0", PSP0)
+defExistingVar("RSP0", RSP0)
+STATE = defNewVar("STATE", 0)
+BASE = 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 NEXT
+    return mem[NEXT]
 end)
 
 FROMR = defPrim("R>", () -> begin
     pushPS(popRS())
-    return NEXT
+    return mem[NEXT]
 end)
 
 RSPFETCH = defPrim("RSP@", () -> begin
-    pushPS(RSP)
-    return NEXT
+    pushPS(reg.RSP)
+    return mem[NEXT]
 end)
 
 RSPSTORE = defPrim("RSP!", () -> begin
     RSP = popPS()
-    return NEXT
+    return mem[NEXT]
 end)
 
 RDROP = defPrim("RDROP", () -> begin
     popRS()
-    return NEXT
+    return mem[NEXT]
 end)
 
 # Parameter Stack
 
 PSPFETCH = defPrim("PSP@", () -> begin
-    pushPS(PSP)
-    return NEXT
+    pushPS(reg.PSP)
+    return mem[NEXT]
 end)
 
 PSPSTORE = defPrim("PSP!", () -> begin
     PSP = popPS()
-    return NEXT
+    return mem[NEXT]
 end)
 
 # I/O
 
-defConst("TIB", tib)
-defVar("#TIB", :numtib)
-defVar(">IN", :toin)
+defConst("TIB", TIB)
+NUMTIB = defNewVar("#TIB", 0)
+TOIN = defNewVar(">IN", 0)
 
 KEY = defPrim("KEY", () -> begin
-    if toin >= numtib
-
+    if mem[TOIN] >= mem[NUMTIB]
+        mem[TOIN] = 0
+        line = readline()
+        mem[NUMTIB] = length(line)
+        putString(line, TIB)
     end
 
-    return NEXT
+    pushPS(mem[TIB + mem[TOIN]])
+    mem[TOIN] += 1
+
+    return mem[NEXT]
 end)
 
 EMIT = defPrim("EMIT", () -> begin
-
-    return NEXT
+    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
 
-    return NEXT
+    while true
+        mem[wordAddr + offset] = Int64(c)
+        offset += 1
+
+        callPrim(mem[KEY])
+        c = Char(popPS())
+
+        if c == ' ' || c == '\t' || c == '\n'
+            break
+        end
+    end
+
+    wordLen = offset
+
+    pushPS(wordAddr)
+    pushPS(wordLen)
+
+    return mem[NEXT]
 end)
 
 NUMBER = defPrim("NUMBER", () -> begin
 
-    return NEXT
+    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 = 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 = getString(thisAddr, len)
+
+        if thisWord == 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)
 
 #### VM loop ####
 function runVM()
-    jmp = NEXT
+    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)
+
+    for i in 0:(count-1)
+        addr = startAddr + i
+        if i%cellsPerLine == 0
+            print("$addr:")
+        end
+
+        print("\t$(mem[addr]) ")
+
+        if (mem[addr]>=32 && mem[addr]<128)
+            chars[i%cellsPerLine + 1] = Char(mem[addr])
+        else
+            chars[i%cellsPerLine + 1] = '.'
+        end
+
+        if i%cellsPerLine == cellsPerLine-1
+            println(string("\t", ASCIIString(chars)))
+        end
+    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