X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=src%2Fforth.jl;h=766bd4e1cdf2f3ff24685ab186a75188103f8202;hb=4b2f52917ce00e4af92d2a3a86e199d21748da5b;hp=a3c55f04309c2b07b4d622b2638c78747a1d8c25;hpb=892ce90d5c9975c154800002ddfcb6d7c82910a0;p=forth.jl.git

diff --git a/src/forth.jl b/src/forth.jl
index a3c55f0..766bd4e 100644
--- a/src/forth.jl
+++ b/src/forth.jl
@@ -1,12 +1,12 @@
 module forth
 
 # VM mem size
-size_mem = 640*1024
+size_mem = 1000000 # 1 mega-int
 
 # Buffer sizes
-size_RS = 1024   # Return stack size
-size_PS = 1024   # Parameter stack size
-size_TIB = 1096  # Terminal input buffer size
+size_RS = 1000   # Return stack size
+size_PS = 1000   # Parameter stack size
+size_TIB = 1000  # Terminal input buffer size
 
 # The mem array constitutes the memory of the VM. It has the following geography:
 #
@@ -55,27 +55,29 @@ type Reg
     PSP::Int64  # Parameter/data stack pointer
     IP::Int64   # Instruction pointer
     W::Int64    # Working register
-
-    source::Any # Input stream in use
 end
-reg = Reg(mem[RSP0], mem[PSP0], 0, 0, STDIN)
+reg = Reg(mem[RSP0], mem[PSP0], 0, 0)
 
 # Stack manipulation functions
 
-type StackUnderflow <: Exception end
+type ParamStackUnderflow <: Exception end
+type ReturnStackUnderflow <: Exception end
+
+Base.showerror(io::IO, ex::ParamStackUnderflow) = print(io, "Parameter stack underflow.")
+Base.showerror(io::IO, ex::ReturnStackUnderflow) = print(io, "Return stack underflow.")
 
 getRSDepth() = reg.RSP - mem[RSP0]
 getPSDepth() = reg.PSP - mem[PSP0]
 
 function ensurePSDepth(depth::Int64)
     if getPSDepth()<depth
-        throw(StackUnderflow())
+        throw(ParamStackUnderflow())
     end
 end
 
 function ensureRSDepth(depth::Int64)
     if getRSDepth()<depth
-        throw(StackUnderflow())
+        throw(ReturnStackUnderflow())
     end
 end
 
@@ -114,14 +116,25 @@ end
 
 function defPrim(f::Function; name="nameless")
     push!(primitives, f)
-    push!(primNames, name)
+    push!(primNames, replace(replace(name, "\004", "EOF"), "\n", "\\n"))
 
     return -length(primitives)
 end
 
-callPrim(addr::Int64) = primitives[-addr]()
+function callPrim(addr::Int64)
+    if addr >=0 || -addr>length(primitives)
+        error("Attempted to execute non-existent primitive at address $addr.")
+    else
+        primitives[-addr]()
+    end
+end
+getPrimName(addr::Int64) = primNames[-addr]
 
-# Word creation
+# Word creation functions
+
+F_IMMED = 128
+F_HIDDEN = 256
+F_LENMASK = 127
 
 function createHeader(name::AbstractString, flags::Int64)
     mem[mem[HERE]] = mem[LATEST]
@@ -157,7 +170,7 @@ function defWord(name::AbstractString, wordAddrs::Array{Int64,1}; flags::Int64=0
     return addr
 end
 
-# Variable creation
+# Variable creation functions
 
 function defExistingVar(name::AbstractString, varAddr::Int64; flags::Int64=0)
 
@@ -173,24 +186,21 @@ function defNewVar(name::AbstractString, initial::Int64; flags::Int64=0)
     codeWordAddr = mem[HERE]
     varAddr = mem[HERE] + 1
 
-    f = eval(:(() -> begin
-        pushPS($(varAddr))
-        return NEXT
-    end))
-
-    mem[mem[HERE]] = defPrim(f, name=name); 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)
-    defPrimWord(name, eval(:(() -> begin
-        pushPS($(val))
-        return NEXT
-    end)))
+    createHeader(name, flags)
 
-    return val
+    codeWordAddr = mem[HERE]
+
+    mem[mem[HERE]] = DOCON; mem[HERE] += 1
+    mem[mem[HERE]] = val; mem[HERE] += 1
+
+    return codeWordAddr
 end
 
 # Threading Primitives (inner interpreter)
@@ -207,11 +217,39 @@ DOCOL = defPrim(() -> begin
     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_CFA = defConst("F_IMMED", F_IMMED)
+F_HIDDEN_CFA = defConst("F_HIDDEN", F_HIDDEN)
+F_LENMASK_CFA = defConst("F_LENMASK", F_LENMASK)
+
 # Basic forth primitives
 
 DROP = defPrimWord("DROP", () -> begin
@@ -228,6 +266,7 @@ SWAP = defPrimWord("SWAP", () -> begin
 end)
 
 DUP = defPrimWord("DUP", () -> begin
+    ensurePSDepth(1)
     pushPS(mem[reg.PSP])
     return NEXT
 end)
@@ -242,9 +281,9 @@ ROT = defPrimWord("ROT", () -> begin
     a = popPS()
     b = popPS()
     c = popPS()
+    pushPS(b)
     pushPS(a)
     pushPS(c)
-    pushPS(b)
     return NEXT
 end)
 
@@ -252,12 +291,13 @@ NROT = defPrimWord("-ROT", () -> begin
     a = popPS()
     b = popPS()
     c = popPS()
-    pushPS(b)
     pushPS(a)
     pushPS(c)
+    pushPS(b)
     return NEXT
 end)
 
+
 TWODROP = defPrimWord("2DROP", () -> begin
     popPS()
     popPS()
@@ -280,8 +320,17 @@ TWOSWAP = defPrimWord("2SWAP", () -> begin
     d = popPS()
     pushPS(b)
     pushPS(a)
-    pushPS(c)
     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)
 
@@ -348,14 +397,24 @@ DIVMOD = defPrimWord("/MOD", () -> begin
     return NEXT
 end)
 
-EQU = defPrimWord("=", () -> begin
+TWOMUL = defPrimWord("2*", () -> begin
+    pushPS(popPS() << 1)
+    return NEXT
+end)
+
+TWODIV = defPrimWord("2/", () -> begin
+    pushPS(popPS() >> 1)
+    return NEXT
+end)
+
+EQ = defPrimWord("=", () -> begin
     b = popPS()
     a = popPS()
     pushPS(a==b ? -1 : 0)
     return NEXT
 end)
 
-NEQU = defPrimWord("<>", () -> begin
+NE = defPrimWord("<>", () -> begin
     b = popPS()
     a = popPS()
     pushPS(a!=b ? -1 : 0)
@@ -390,12 +449,12 @@ GE = defPrimWord(">=", () -> begin
     return NEXT
 end)
 
-ZEQU = defPrimWord("0=", () -> begin
+ZE = defPrimWord("0=", () -> begin
     pushPS(popPS() == 0 ? -1 : 0)
     return NEXT
 end)
 
-ZNEQU = defPrimWord("0<>", () -> begin
+ZNE = defPrimWord("0<>", () -> begin
     pushPS(popPS() != 0 ? -1 : 0)
     return NEXT
 end)
@@ -484,24 +543,6 @@ SUBSTORE = defPrimWord("-!", () -> begin
 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 = defPrimWord(">R", () -> begin
@@ -514,6 +555,11 @@ FROMR = defPrimWord("R>", () -> begin
     return NEXT
 end)
 
+RFETCH = defPrimWord("R@", () -> begin
+    pushPS(mem[reg.RSP])
+    return NEXT
+end)
+
 RSPFETCH = defPrimWord("RSP@", () -> begin
     pushPS(reg.RSP)
     return NEXT
@@ -555,110 +601,41 @@ end)
 
 # I/O
 
-defConst("TIB", TIB)
-NUMTIB, NUMTIB_CFA = defNewVar("#TIB", 0)
-TOIN, TOIN_CFA = defNewVar(">IN", 0)
-
-KEY = defPrimWord("KEY", () -> begin
-    if mem[TOIN] >= mem[NUMTIB]
-        mem[TOIN] = 0
-
-        if reg.source != STDIN && eof(reg.source)
-            reg.source = STDIN
-        end
-
-        line = readline(reg.source)
-        mem[NUMTIB] = length(line)
-        putString(line, TIB)
-    end
+sources = Array{Any,1}()
+currentSource() = sources[length(sources)]
 
-    pushPS(mem[TIB + mem[TOIN]])
-    mem[TOIN] += 1
-
-    return NEXT
-end)
+EOF_CFA = defConst("EOF", 4)
 
 EMIT = defPrimWord("EMIT", () -> begin
     print(Char(popPS()))
     return NEXT
 end)
 
-WORD = defPrimWord("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 NEXT
-    end
-
-    while true
-        mem[wordAddr + offset] = Int64(c)
-        offset += 1
-
-        callPrim(mem[KEY])
-        c = Char(popPS())
+SPAN, SPAN_CFA = defNewVar("SPAN", 0)
+EXPECT = defPrimWord("EXPECT", () -> begin
+    maxLen = popPS()
+    addr = popPS()
 
-        if c == ' ' || c == '\t' || c == '\n'
-            # Rewind KEY
-            mem[TOIN] -= 1
-            break
-        end
+    if !eof(currentSource())
+        line = chomp(readline(currentSource()))
+        mem[SPAN] = min(length(line), maxLen)
+        putString(line[1:mem[SPAN]], addr)
+    else
+        mem[SPAN] = 1
+        mem[addr] = EOF
     end
 
-    wordLen = offset
-
-    pushPS(wordAddr)
-    pushPS(wordLen)
-
     return NEXT
 end)
 
+BASE, BASE_CFA = defNewVar("BASE", 10)
 NUMBER = defPrimWord("NUMBER", () -> begin
-
-    wordLen = popPS()
-    wordAddr = popPS()
+    wordAddr = popPS()+1
+    wordLen = mem[wordAddr-1]
 
     s = getString(wordAddr, wordLen)
 
-    try
-        pushPS(parse(Int64, s, mem[BASE]))
-        pushPS(0)
-    catch
-        pushPS(1) # Error indication
-    end
+    pushPS(parse(Int64, s, mem[BASE]))
 
     return NEXT
 end)
@@ -667,8 +644,9 @@ end)
 
 FIND = defPrimWord("FIND", () -> begin
 
-    wordLen = popPS()
-    wordAddr = popPS()
+    countedAddr = popPS()
+    wordAddr = countedAddr + 1
+    wordLen = mem[countedAddr]
     word = lowercase(getString(wordAddr, wordLen))
 
     latest = LATEST
@@ -707,71 +685,7 @@ TOCFA = defPrimWord(">CFA", () -> begin
     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])
+TOPFA = defWord(">PFA", [TOCFA, INCR, EXIT])
 
 # Branching
 
@@ -802,7 +716,7 @@ LITSTRING = defPrimWord("LITSTRING", () -> begin
     return NEXT
 end)
 
-TELL = defPrimWord("TELL", () -> begin
+TYPE = defPrimWord("TYPE", () -> begin
     len = popPS()
     addr = popPS()
     str = getString(addr, len)
@@ -812,121 +726,279 @@ end)
 
 # Outer interpreter
 
+TRACE = defPrimWord("TRACE", () -> begin
+    println("reg.W: $(reg.W) reg.IP: $(reg.IP)")
+    print("PS: "); printPS()
+    print("RS: "); printRS()
+    print("[paused]")
+    readline()
+
+    return NEXT
+end)
+
+COMMA = defPrimWord(",", () -> begin
+    mem[mem[HERE]] = popPS()
+    mem[HERE] += 1
+
+    return NEXT
+end)
+
+BTICK = defWord("[']",
+    [FROMR, DUP, INCR, TOR, FETCH, EXIT])
+
 EXECUTE = defPrimWord("EXECUTE", () -> begin
     reg.W = popPS()
     return mem[reg.W]
 end)
 
-INTERPRET = defPrimWord("INTERPRET", () -> begin
+TIB_CFA = defConst("TIB", TIB)
+NUMTIB, NUMTIB_CFA = defNewVar("#TIB", 0)
+TOIN, TOIN_CFA = defNewVar(">IN", 0)
+
+QUERY = defWord("QUERY",
+    [TIB_CFA, LIT, 80, EXPECT,
+    SPAN_CFA, FETCH, NUMTIB_CFA, STORE,
+    LIT, 0, TOIN_CFA, STORE,
+    EXIT])
 
-    callPrim(mem[WORD])
+WORD = defPrimWord("WORD", () -> begin
+    delim = popPS()
 
-    wordName = getString(mem[reg.PSP-1], mem[reg.PSP])
-    #println("... ", replace(wordName, "\n", "\\n"), " ...")
+    # Chew up initial occurrences of delim
+    while (mem[TOIN]<mem[NUMTIB] && mem[TIB+mem[TOIN]] == delim)
+        mem[TOIN] += 1
+    end
 
-    callPrim(mem[TWODUP])
-    callPrim(mem[FIND])
+    countAddr = mem[HERE]
+    addr = mem[HERE]+1
 
-    wordAddr = mem[reg.PSP]
+    # Start reading in word
+    count = 0
+    while (mem[TOIN]<mem[NUMTIB])
+        mem[addr] = mem[TIB+mem[TOIN]]
+        mem[TOIN] += 1
 
-    if wordAddr>0
-        # Word in dictionary
+        if (mem[addr] == delim)
+            break
+        end
 
-        isImmediate = (mem[wordAddr+1] & F_IMMED) != 0
-        callPrim(mem[TOCFA])
+        count += 1
+        addr += 1
+    end
 
-        callPrim(mem[ROT]) # get rid of extra copy of word string details
-        popPS()
-        popPS()
+    # Record count
+    mem[countAddr] = count
+    pushPS(countAddr)
 
-        if mem[STATE] == 0 || isImmediate
-            # Execute!
-            #println("Executing CFA at $(mem[reg.PSP])")
-            return callPrim(mem[EXECUTE])
-        else
-            # Append CFA to dictionary
-            callPrim(mem[COMMA])
-        end
-    else
-        # Not in dictionary, assume number
+    return NEXT
+end)
 
-        popPS()
+PARSE = defPrimWord("PARSE", () -> begin
+    delim = popPS()
 
-        callPrim(mem[NUMBER])
+    # Chew up initial occurrences of delim
+    addr = mem[HERE]
 
-        if popPS() != 0
-            println("Parse error at word: '$wordName'")
-            return NEXT
-        end
+    # Start reading input stream
+    count = 0
+    while (mem[TOIN]<mem[NUMTIB])
+        mem[addr] = mem[TIB+mem[TOIN]]
+        mem[TOIN] += 1
 
-        if mem[STATE] == 0
-            # Number already on stack!
-        else
-            # Append literal to dictionary
-            pushPS(LIT)
-            callPrim(mem[COMMA])
-            callPrim(mem[COMMA])
+        if (mem[addr] == delim)
+            break
         end
+
+        count += 1
+        addr += 1
     end
 
+    pushPS(addr)
+    pushPS(count)
+
     return NEXT
 end)
 
-QUIT = defWord("QUIT",
-    [RSP0_CFA, RSPSTORE,
-    INTERPRET,
-    BRANCH,-2])
-
 BYE = defPrimWord("BYE", () -> begin
+    println("Bye!")
     return 0
 end)
 
-NL = defPrimWord("\n", () -> begin
-    if mem[STATE] == 0
+STATE, STATE_CFA = defNewVar("STATE", 0)
+
+INTERPRET = defWord("INTERPRET",
+    [LIT, 32, WORD, # Read next space-delimited word
+
+    DUP, FETCH, ZE, ZBRANCH, 3,
+        DROP, EXIT, # Exit if TIB is exhausted
+
+    STATE_CFA, FETCH, ZBRANCH, 31,
+        # Compiling
+        DUP, FIND, QDUP, ZBRANCH, 19,
+
+            # Found word. 
+            SWAP, DROP,
+            DUP, TOCFA, SWAP, INCR, FETCH, LIT, F_IMMED, AND, ZBRANCH, 4,
+                # Immediate: Execute!
+                EXECUTE, BRANCH, -33,
+
+                # Not immediate: Compile!
+                COMMA, BRANCH, -36,
+
+            # No word found, parse number
+            NUMBER, BTICK, LIT, COMMA, COMMA, BRANCH, -43,
+        
+       # Interpreting
+        DUP, FIND, QDUP, ZBRANCH, 7,
+
+            # Found word. Execute!
+            SWAP, DROP, TOCFA, EXECUTE, BRANCH, -54,
+
+            # No word found, parse number and leave on stack
+            NUMBER, BRANCH, -57,
+    EXIT]
+)
+
+PROMPT = defPrimWord("PROMPT", () -> begin
+    if (mem[STATE] == 0 && currentSource() == STDIN)
         println(" ok")
     end
+
     return NEXT
-end, flags=F_IMMED)
+end)
 
-# Odds and Ends
+QUIT = defWord("QUIT",
+    [RSP0_CFA, RSPSTORE,
+    QUERY,
+    INTERPRET, PROMPT,
+    BRANCH,-4])
 
-CHAR = defPrimWord("CHAR", () -> begin
+INCLUDE = defPrimWord("INCLUDE", () -> begin
+    pushPS(32)
     callPrim(mem[WORD])
-    wordLen = popPS()
-    wordAddr = popPS()
+    wordAddr = popPS()+1
+    wordLen = mem[wordAddr-1]
     word = getString(wordAddr, wordLen)
-    pushPS(Int64(word[1]))
+
+    push!(sources, open(word, "r"))
+
+    # Clear input buffer
+    mem[NUMTIB] = 0
 
     return NEXT
 end)
 
-INCLUDE = defPrimWord("INCLUDE", () -> begin
+# Compilation
 
-    callPrim(mem[WORD])
-    wordLen = popPS()
-    wordAddr = popPS()
+HEADER = defPrimWord("HEADER", () -> begin
+    wordAddr = popPS()+1
+    wordLen = mem[wordAddr-1]
     word = getString(wordAddr, wordLen)
 
-    println("Reading from $word...")
+    createHeader(word, 0)
 
-    reg.source = open(word, "r")
+    return NEXT
+end)
 
-    # Clear input buffer
-    mem[NUMTIB] = 0
+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",
+    [LIT, 32, WORD,
+    FIND,
+    HIDDEN,
+    EXIT])
+
+COLON = defWord(":",
+    [LIT, 32, 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)
+
+
 #### VM loop ####
-function run()
+
+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
+
+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 = callPrim(jmp)) != 0
-        #println("Evaluating prim $jmp [$(primNames[-jmp])]")
+    while jmp != 0
+        try
+            #println("Entering prim $(getPrimName(jmp))")
+            jmp = callPrim(jmp)
+
+        catch ex
+            showerror(STDOUT, ex)
+            println()
+
+            while !isempty(sources) && currentSource() != STDIN
+                close(pop!(sources))
+            end
+
+            # Want backtrace in here eventually
+            println("reg.W: $(reg.W) reg.IP: $(reg.IP)")
+            print("PS: "); printPS()
+            print("RS: "); printRS()
+
+            mem[STATE] = 0
+            mem[NUMTIB] = 0
+            reg.PSP = mem[PSP0]
+            reg.RSP = mem[RSP0]
+            reg.IP = QUIT + 1
+            jmp = NEXT
+        end
     end
 end
 
@@ -993,4 +1065,13 @@ function printRS()
     end
 end
 
+DUMP = defPrimWord("DUMP", () -> begin
+    count = popPS()
+    addr = popPS()
+
+    dump(addr, count=count)
+
+    return NEXT
+end)
+
 end