X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=src%2Fforth.jl;h=b1d782ce1d11a0e6d291083315532922ea43c51c;hb=d2b2b3e5b33f882c18c9e7cf8c6623f4e863c2dd;hp=0aee7fb47a87da7081f93fe3453235e8a38c9d3f;hpb=f6bffd243af0e9ac05198c5ea43c21c2341a5cfa;p=forth.jl.git

diff --git a/src/forth.jl b/src/forth.jl
index 0aee7fb..b1d782c 100644
--- a/src/forth.jl
+++ b/src/forth.jl
@@ -1,184 +1,1130 @@
 module forth
 
-RS = Array{Int64, 1}(1024)
-RSP = 0
+# VM mem size
+size_mem = 1000000 # 1 mega-int
 
-PS = Array{Int64, 1}(1024)
-PSP =0
+# Buffer sizes
+size_RS = 1000   # Return stack size
+size_PS = 1000   # Parameter stack size
+size_TIB = 1000  # Terminal input buffer size
 
-IP = 0
-W = 0
-X = 0
+# 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 as negative indicies
+# into the primitives array which contains these functions.
 
-jmp = 0
+mem = Array{Int64,1}(size_mem)
+primitives = Array{Function,1}()
+primNames = Array{ASCIIString,1}()
 
-primitives = Array{Expr,1}()
-memory = Array{Int64,1}(64*1024)
-LATEST = 0
-HERE = 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
 
-# Intperpreter state
+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
+end
+reg = Reg(mem[RSP0], mem[PSP0], 0, 0)
 
-STATE = 0
+# Stack manipulation functions
 
-# Current radix
+type ParamStackUnderflow <: Exception end
+type ReturnStackUnderflow <: Exception end
 
-BASE = 10
+Base.showerror(io::IO, ex::ParamStackUnderflow) = print(io, "Parameter stack underflow.")
+Base.showerror(io::IO, ex::ReturnStackUnderflow) = print(io, "Return stack underflow.")
 
-# Stack manipulation macros
+getRSDepth() = reg.RSP - mem[RSP0]
+getPSDepth() = reg.PSP - mem[PSP0]
+
+function ensurePSDepth(depth::Int64)
+    if getPSDepth()<depth
+        throw(ParamStackUnderflow())
+    end
+end
+
+function ensureRSDepth(depth::Int64)
+    if getRSDepth()<depth
+        throw(ReturnStackUnderflow())
+    end
+end
 
 function pushRS(val::Int64)
-    global RSP
-    RS[RSP += 1] = val
+    mem[reg.RSP+=1] = val
 end
 
 function popRS()
-    global RSP
-    val = RS[RSP]
-    RSP -= 1
+    ensureRSDepth(1)
+
+    val = mem[reg.RSP]
+    reg.RSP -= 1
     return val
 end
 
 function pushPS(val::Int64)
-    global PSP
-    PS[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
 
-# Primitive creation functions
+# Handy functions for adding/retrieving strings to/from memory.
 
-function defPrim(name::AbstractString, expr::Expr)
-    global HERE, LATEST
+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
 
-    memory[HERE] = LATEST
-    LATEST = HERE
-    HERE += 1
+function defPrim(f::Function; name="nameless")
+    push!(primitives, f)
+    push!(primNames, replace(replace(name, "\004", "EOF"), "\n", "\\n"))
+
+    return -length(primitives)
+end
 
-    memory[HERE] = length(name); HERE += 1
-    memory[HERE:(HERE+length(name)-1)] = [Int(c) for c in name]; HERE += length(name)
+callPrim(addr::Int64) = primitives[-addr]()
 
-    push!(primitives, expr)
-    memory[HERE] = -length(primitives)
-    codeword = HERE
-    HERE += 1
+# Word creation functions
 
-    return codeword
+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
 
-defVar(name::AbstractString, var::Expr) = defPrim(name, Expr(:call, :pushPS, var))
-defConst(name::AbstractString, val::Int64) = defPrim(name, Expr(:call, :pushPS, :val))
+function defPrimWord(name::AbstractString, f::Function; flags::Int64=0)
+    createHeader(name, flags)
 
-# Threading Primitives
+    codeWordAddr = mem[HERE]
+    mem[codeWordAddr] = defPrim(f, name=name)
+    mem[HERE] += 1
 
-NEXT = defPrim("NEXT", :(begin
-    W = memory[IP]
-    IP += 1
-    X = memory[W]
-    jmp = X
-end))
+    return codeWordAddr
+end
 
-DOCOL = defPrim("DOCOL", :(begin
-    pushRS(IP)
-    IP = W + 1
-    jmp = NEXT
-end))
+function defWord(name::AbstractString, wordAddrs::Array{Int64,1}; flags::Int64=0)
+    createHeader(name, flags)
 
-EXIT = defPrim("EXIT", :(begin
-    IP = popRS()
-    jmp = NEXT
-end))
+    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 functions
+
+function defExistingVar(name::AbstractString, varAddr::Int64; flags::Int64=0)
+
+    defPrimWord(name, eval(:(() -> begin
+        pushPS($(varAddr))
+        return NEXT
+    end)))
+end
+
+function defNewVar(name::AbstractString, initial::Int64; flags::Int64=0)
+    createHeader(name, flags)
+    
+    codeWordAddr = mem[HERE]
+    varAddr = mem[HERE] + 1
+
+    mem[mem[HERE]] = DOVAR; mem[HERE] += 1
+    mem[mem[HERE]] = initial; mem[HERE] += 1
+
+    return varAddr, codeWordAddr
+end
 
+function defConst(name::AbstractString, val::Int64; flags::Int64=0)
+    createHeader(name, flags)
+
+    mem[mem[HERE]] = DOCON; mem[HERE] += 1
+    mem[mem[HERE]] = val; mem[HERE] += 1
+
+    return val
+end
+
+# Threading Primitives (inner interpreter)
+
+NEXT = defPrim(() -> begin
+    reg.W = mem[reg.IP]
+    reg.IP += 1
+    return mem[reg.W]
+end, name="NEXT")
+
+DOCOL = defPrim(() -> begin
+    pushRS(reg.IP)
+    reg.IP = reg.W + 1
+    return NEXT
+end, name="DOCOL")
+
+DOVAR = defPrim(() -> begin
+    pushPS(reg.W + 1)
+    return NEXT
+end, name="DOVAR")
+
+DOCON = defPrim(() -> begin
+    pushPS(mem[reg.W + 1])
+    return NEXT
+end, name="DOVAR")
+
+EXIT = defPrimWord("EXIT", () -> begin
+    reg.IP = popRS()
+    return NEXT
+end)
+
+# Dictionary entries for core built-in variables, constants
+
+HERE_CFA = defExistingVar("HERE", HERE)
+LATEST_CFA = defExistingVar("LATEST", LATEST)
+PSP0_CFA = defExistingVar("PSP0", PSP0)
+RSP0_CFA = defExistingVar("RSP0", RSP0)
+
+defConst("DOCOL", DOCOL)
+defConst("DOCON", DOCON)
+defConst("DOVAR", DOVAR)
+
+defConst("DICT", DICT)
+defConst("MEMSIZE", size_mem)
+
+F_IMMED = defConst("F_IMMED", 128)
+F_HIDDEN = defConst("F_HIDDEN", 256)
+F_LENMASK = defConst("F_LENMASK", 127)
 
 # Basic forth primitives
 
-DROP = defPrim("DROP", :(begin
+DROP = defPrimWord("DROP", () -> begin
     popPS()
-    jmp = NEXT
-end))
+    return NEXT
+end)
 
-SWAP = defPrim("SWAP", :(begin
-    PS[PSP], PS[PSP-1] = PS[PSP-1], PS[PS]
-    jmp = NEXT
-end))
+SWAP = defPrimWord("SWAP", () -> begin
+    a = popPS()
+    b = popPS()
+    pushPS(a)
+    pushPS(b)
+    return NEXT
+end)
 
-DUP = defPrim("DUP", :(begin
-    pushPS(PS[PSP])
-    jmp = NEXT
-end))
+DUP = defPrimWord("DUP", () -> begin
+    ensurePSDepth(1)
+    pushPS(mem[reg.PSP])
+    return NEXT
+end)
 
-LIT = defPrim("LIT", :(begin
-    pushPS(memory[IP])
-    IP += 1
-    jmp = NEXT
-end))
+OVER = defPrimWord("OVER", () -> begin
+    ensurePSDepth(2)
+    pushPS(mem[reg.PSP-1])
+    return NEXT
+end)
+
+ROT = defPrimWord("ROT", () -> begin
+    a = popPS()
+    b = popPS()
+    c = popPS()
+    pushPS(b)
+    pushPS(a)
+    pushPS(c)
+    return NEXT
+end)
+
+NROT = defPrimWord("-ROT", () -> begin
+    a = popPS()
+    b = popPS()
+    c = popPS()
+    pushPS(a)
+    pushPS(c)
+    pushPS(b)
+    return NEXT
+end)
+
+
+TWODROP = defPrimWord("2DROP", () -> begin
+    popPS()
+    popPS()
+    return NEXT
+end)
+
+TWODUP = defPrimWord("2DUP", () -> begin
+    ensurePSDepth(2)
+    a = mem[reg.PSP-1]
+    b = mem[reg.PSP]
+    pushPS(a)
+    pushPS(b)
+    return NEXT
+end)
+
+TWOSWAP = defPrimWord("2SWAP", () -> begin
+    a = popPS()
+    b = popPS()
+    c = popPS()
+    d = popPS()
+    pushPS(b)
+    pushPS(a)
+    pushPS(d)
+    pushPS(c)
+    return NEXT
+end)
+
+TWOOVER = defPrimWord("2OVER", () -> begin
+    ensurePSDepth(4)
+    a = mem[reg.PSP-3]
+    b = mem[reg.PSP-2]
+    pushPS(a)
+    pushPS(b)
+    return NEXT
+end)
+
+QDUP = defPrimWord("?DUP", () -> begin
+    ensurePSDepth(1)
+    val = mem[reg.PSP]
+    if val != 0
+        pushPS(val)
+    end
+    return NEXT
+end)
+
+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)
+
+TWOMUL = defPrimWord("2*", () -> begin
+    pushPS(popPS() << 1)
+    return NEXT
+end)
+
+TWODIV = defPrimWord("2/", () -> begin
+    pushPS(popPS() >> 1)
+    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
+end)
 
 # Memory primitives
 
-STORE = defPrim("!", :(begin
+STORE = defPrimWord("!", () -> begin
     addr = popPS()
     dat = popPS()
-    memory[addr] = dat
-    jmp = NEXT
-end))
+    mem[addr] = dat
+    return NEXT
+end)
 
-FETCH = defPrim("@", :(begin
+FETCH = defPrimWord("@", () -> begin
     addr = popPS()
-    pushPS(memory[addr])
-    jmp = NEXT
-end))
+    pushPS(mem[addr])
+    return NEXT
+end)
 
-ADDSTORE = defPrim("+!", :(begin
+ADDSTORE = defPrimWord("+!", () -> begin
     addr = popPS()
     toAdd = popPS()
-    memory[addr] += toAdd
-    jmp = NEXT
-end))
+    mem[addr] += toAdd
+    return NEXT
+end)
 
-SUBSTORE = defPrim("-!", :(begin
+SUBSTORE = defPrimWord("-!", () -> begin
     addr = popPS()
     toSub = popPS()
-    memory[addr] -= toSub
-    jmp = NEXT
-end))
+    mem[addr] -= toSub
+    return NEXT
+end)
 
 
-# Built-in variables
+# Return Stack
 
-defVar("STATE", :STATE)
-defVar("HERE", :HERE)
-defVar("LATEST", :LATEST)
-defVAR("BASE", :BASE)
+TOR = defPrimWord(">R", () -> begin
+    pushRS(popPS())
+    return NEXT
+end)
 
-# Constants
+FROMR = defPrimWord("R>", () -> begin
+    pushPS(popRS())
+    return NEXT
+end)
 
-defConst("VERSION", 1)
-defConst("DOCOL", DOCOL)
+RFETCH = defPrimWord("R@", () -> begin
+    pushPS(mem[reg.RSP])
+    return NEXT
+end)
 
-# Return Stack
+RSPFETCH = defPrimWord("RSP@", () -> begin
+    pushPS(reg.RSP)
+    return NEXT
+end)
 
-TOR = defPrim(">R", :(pushRS(popPS())))
-FROMR = defPrim("R>", :(pushPS(popRS())))
-RSPFETCH = defPrim("RSP@", :(pushPS(RSP)))
-RSPSTORE = defPrim("RSP!", :(RSP = popPS()))
-RDROP = defPrim("RDROP", :(popRS()))
+RSPSTORE = defPrimWord("RSP!", () -> begin
+    RSP = popPS()
+    return NEXT
+end)
+
+RDROP = defPrimWord("RDROP", () -> begin
+    popRS()
+    return NEXT
+end)
 
 # Parameter Stack
 
-PSPFETCH = defPrim("PSP@", :(pushPS(PSP)))
-PSPSTORE = defPrim("PSP!", :(PSP = popPS()))
+PSPFETCH = defPrimWord("PSP@", () -> begin
+    pushPS(reg.PSP)
+    return NEXT
+end)
+
+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
+
+sources = Array{Any,1}()
+currentSource() = sources[length(sources)]
+
+defConst("TIB", TIB)
+NUMTIB, NUMTIB_CFA = defNewVar("#TIB", 0)
+TOIN, TOIN_CFA = defNewVar(">IN", 0)
+EOF = defConst("EOF", 4)
+
+KEY = defPrimWord("KEY", () -> begin
+    if mem[TOIN] >= mem[NUMTIB]
+        mem[TOIN] = 0
+
+        if !eof(currentSource())
+            line = readline(currentSource())
+            mem[NUMTIB] = length(line)
+            putString(line, TIB)
+        else
+            mem[NUMTIB] = 1
+            mem[TIB] = EOF
+        end
+    end
+
+    pushPS(mem[TIB + mem[TOIN]])
+    mem[TOIN] += 1
+
+    return NEXT
+end)
+
+EMIT = defPrimWord("EMIT", () -> begin
+    print(Char(popPS()))
+    return NEXT
+end)
+
+WORD = defPrimWord("WORD", () -> begin
+
+    eof_char = Char(EOF)
+    c = eof_char
+
+    while true
+        callPrim(mem[KEY])
+        c = Char(popPS())
+
+        if c == ' ' || c == '\t'
+            continue
+        end
+
+        break
+    end
+
+    wordAddr = mem[HERE]
+    offset = 0
+
+    if c == '\n' || c == eof_char
+        # Treat newline as a special word
+
+        mem[wordAddr + offset] = Int64(c)
+        pushPS(wordAddr)
+        pushPS(1)
+        return NEXT
+    end
 
-# VM loop
-jmp = NEXT
-function runVM()
     while true
-        eval(primitives[-memory[jmp]])
+        mem[wordAddr + offset] = Int64(c)
+        offset += 1
+
+        callPrim(mem[KEY])
+        c = Char(popPS())
+
+        if c == ' ' || c == '\t' || c == '\n' || c == eof_char
+            # Rewind KEY
+            mem[TOIN] -= 1
+            break
+        end
     end
+
+    wordLen = offset
+
+    pushPS(wordAddr)
+    pushPS(wordLen)
+
+    return NEXT
+end)
+
+BASE, BASE_CFA = defNewVar("BASE", 10)
+NUMBER = defPrimWord("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 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))
+
+        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])
+
+# 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
+
+    return NEXT
+end)
+
+# Compilation
+
+STATE, STATE_CFA = defNewVar("STATE", 0)
+
+HEADER = defPrimWord("HEADER", () -> 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,
+    HEADER,
+    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])
+
+BTICK = defWord("[']",
+    [FROMR, DUP, INCR, TOR, FETCH, EXIT])
+
+# CREATE and DOES>
+
+CREATE = defWord("CREATE",
+    [WORD,
+    HEADER,
+    LIT, DOVAR, COMMA, EXIT]);
+
+DODOES = defPrim(() -> begin
+    pushRS(reg.IP)
+    reg.IP = reg.W + 1
+    return NEXT
+end, name="DOCOL")
+
+defConst("DODOES", DODOES)
+
+FROMDOES_PAREN = defWord("(DOES>)",
+    [DODOES, LATEST, FETCH, TOCFA, STORE, EXIT])
+
+FROMDOES = defWord("DOES>",
+    [BTICK, FROMDOES_PAREN, COMMA, BTICK, EXIT, COMMA,
+    BTICK, LIT, COMMA, LATEST, FETCH, TODFA, COMMA], flags=F_IMMED)
+    
+
+# 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)
+
+type ParseError <: Exception
+    wordName::ASCIIString
 end
+Base.showerror(io::IO, ex::ParseError) = print(io, "Parse error at word: '$(ex.wordName)'.")
+
+DEBUG, DEBUG_CFA = defNewVar("DEBUG", 0)
+
+INTERPRET = defPrimWord("INTERPRET", () -> begin
+
+    callPrim(mem[WORD])
+
+    wordName = getString(mem[reg.PSP-1], mem[reg.PSP])
+    if mem[DEBUG] != 0
+        println("... ", replace(replace(wordName, "\004", "EOF"), "\n", "\\n"), " ...")
+    end
+
+    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[NROT]) # get rid of extra copy of word string details
+        popPS()
+        popPS()
+
+        if mem[STATE] == 0 || isImmediate
+            # Execute!
+            return callPrim(mem[EXECUTE])
+        else
+            # Append CFA to dictionary
+            callPrim(mem[COMMA])
+        end
+    else
+        # Not in dictionary, assume number
+
+        popPS()
+
+        callPrim(mem[NUMBER])
+
+        if popPS() != 0
+            throw(ParseError(wordName))
+        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])
+
+BYE = defPrimWord("BYE", () -> begin
+    return 0
+end)
+
+PROMPT = defPrimWord("PROMPT", () -> begin
+    println(" ok")
+end)
+
+NL = defPrimWord("\n", () -> begin
+    if mem[STATE] == 0 && currentSource() == STDIN
+        callPrim(mem[PROMPT])
+    end
+    return NEXT
+end, flags=F_IMMED)
+
+INCLUDE = defPrimWord("INCLUDE", () -> begin
+    callPrim(mem[WORD])
+    wordLen = popPS()
+    wordAddr = popPS()
+    word = getString(wordAddr, wordLen)
+
+    push!(sources, open(word, "r"))
+
+    # Clear input buffer
+    mem[NUMTIB] = 0
+
+    return NEXT
+end)
+
+EOF_WORD = defPrimWord("\x04", () -> begin
+    if currentSource() != STDIN
+        close(currentSource())
+    end
+
+    pop!(sources)
+
+    if length(sources)>0
+        if currentSource() == STDIN
+            callPrim(mem[PROMPT])
+        end
+
+        return NEXT
+    else
+        return 0
+    end
+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)
+
+initialized = false
+initFileName = nothing
+if isfile("lib.4th")
+    initFileName = "lib.4th"
+elseif isfile(Pkg.dir("forth/src/lib.4th"))
+    initFileName = Pkg.dir("forth/src/lib.4th")
+end
+
+
+#### VM loop ####
+function run(;initialize=true)
+    # Begin with STDIN as source
+    push!(sources, STDIN)
+
+    global initialized, initFileName
+    if !initialized && initialize
+        if initFileName != nothing
+            print("Including definitions from $initFileName...")
+            push!(sources, open(initFileName, "r"))
+            initialized = true
+        else
+            println("No library file found. Only primitive words available.")
+        end
+    end
+
+    # 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 != 0
+        try
+            if mem[DEBUG] != 0
+                println("Evaluating prim ", jmp," ", primNames[-jmp])
+            end
+
+            jmp = callPrim(jmp)
+
+        catch ex
+            showerror(STDOUT, ex)
+            println()
+
+            while !isempty(sources) && currentSource() != STDIN
+                close(pop!(sources))
+            end
+
+            mem[STATE] = 0
+            mem[NUMTIB] = 0
+            reg.PSP = mem[PSP0]
+            reg.RSP = mem[RSP0]
+            reg.IP = QUIT + 1
+            jmp = NEXT
+        end
+    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
+
+DUMP = defPrimWord("DUMP", () -> begin
+    count = popPS()
+    addr = popPS()
+
+    dump(addr, count=count)
+
+    return NEXT
+end)
 
 end