From: Tim Vaughan Date: Mon, 25 Apr 2016 11:14:44 +0000 (+1200) Subject: Added DO WHILE REPEAT, as well as . and .s X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=commitdiff_plain;h=61231ed1d5237aa1271be30f458acb7e5c773bda;p=forth.jl.git Added DO WHILE REPEAT, as well as . and .s . and .s are now compiled from source, not primitives! --- diff --git a/src/forth.jl b/src/forth.jl index 78d8a53..3a2509b 100644 --- a/src/forth.jl +++ b/src/forth.jl @@ -60,20 +60,24 @@ 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() begin return 0 end) +PROMPT = defPrimWord("PROMPT", () -> begin + println(" ok") +end) + NL = defPrimWord("\n", () -> begin if mem[STATE] == 0 && currentSource() == STDIN - println(" ok") + callPrim(mem[PROMPT]) end return NEXT end, flags=F_IMMED) @@ -917,6 +925,10 @@ EOF_WORD = defPrimWord("\x04", () -> begin pop!(sources) if length(sources)>0 + if currentSource() == STDIN + callPrim(mem[PROMPT]) + end + return NEXT else return 0 @@ -952,15 +964,12 @@ function run() jmp = callPrim(jmp) catch ex - if isa(ex, StackUnderflow) - println("Stack underflow!") + showerror(STDOUT, ex) + println() - mem[NUMTIB] = 0 - reg.IP = QUIT + 1 - jmp = NEXT - else - rethrow(ex) - end + mem[NUMTIB] = 0 + reg.IP = QUIT + 1 + jmp = NEXT end end end @@ -1028,16 +1037,6 @@ function printRS() end end -DOT = defPrimWord(".", () -> begin - print(popPS()) - return NEXT -end) - -#DOTS = defPrimWord(".s", () -> begin -# printPS() -# return NEXT -#end) - DUMP = defPrimWord("DUMP", () -> begin count = popPS() addr = popPS() diff --git a/src/lib.4th b/src/lib.4th index b7cd560..4b60a1e 100644 --- a/src/lib.4th +++ b/src/lib.4th @@ -1,4 +1,4 @@ -: / /MOD SWAP DROP ; +' 1+ , : / /MOD SWAP DROP ; : MOD /MOD DROP ; : '\n' 10 ; @@ -13,25 +13,24 @@ : FALSE 0 ; : NOT 0= ; -: LITERAL IMMEDIATE ' LIT , , ; +: CELLS ; \ Allow for slightly more portable code -: ':' - [ - CHAR : - ] - LITERAL -; +: DEPTH PSP@ PSP0 @ - ; + +: LITERAL IMMEDIATE ' LIT , , ; +: ':' [ CHAR : ] LITERAL ; : ';' [ CHAR ; ] LITERAL ; : '(' [ CHAR ( ] LITERAL ; : ')' [ CHAR ) ] LITERAL ; +: '<' [ CHAR < ] LITERAL ; +: '>' [ CHAR > ] LITERAL ; : '"' [ CHAR " ] LITERAL ; : 'A' [ CHAR A ] LITERAL ; : '0' [ CHAR 0 ] LITERAL ; : '-' [ CHAR - ] LITERAL ; : '.' [ CHAR . ] LITERAL ; -\ While compiling, '[COMPILE] word' compiles 'word' if it would otherwise be IMMEDIATE. : [COMPILE] IMMEDIATE WORD \ get the next word FIND \ find it in the dictionary @@ -39,38 +38,14 @@ , \ and compile that ; -\ RECURSE makes a recursive call to the current word that is being compiled. -\ -\ Normally while a word is being compiled, it is marked HIDDEN so that references to the -\ same word within are calls to the previous definition of the word. However we still have -\ access to the word which we are currently compiling through the LATEST pointer so we -\ can use that to compile a recursive call. : RECURSE IMMEDIATE LATEST @ \ LATEST points to the word being compiled at the moment >CFA \ get the codeword , \ compile it ; -\ CONTROL STRUCTURES ---------------------------------------------------------------------- -\ -\ So far we have defined only very simple definitions. Before we can go further, we really need to -\ make some control structures, like IF ... THEN and loops. Luckily we can define arbitrary control -\ structures directly in FORTH. -\ -\ Please note that the control structures as I have defined them here will only work inside compiled -\ words. If you try to type in expressions using IF, etc. in immediate mode, then they won't work. -\ Making these work in immediate mode is left as an exercise for the reader. - -\ condition IF true-part THEN rest -\ -- compiles to: --> condition 0BRANCH OFFSET true-part rest -\ where OFFSET is the offset of 'rest' -\ condition IF true-part ELSE false-part THEN -\ -- compiles to: --> condition 0BRANCH OFFSET true-part BRANCH OFFSET2 false-part rest -\ where OFFSET if the offset of false-part and OFFSET2 is the offset of rest - -\ IF is an IMMEDIATE word which compiles 0BRANCH followed by a dummy offset, and places -\ the address of the 0BRANCH on the stack. Later when we see THEN, we pop that address -\ off the stack, calculate the offset, and back-fill the offset. +\ CONTROL STRUCTURES ---------------------------------------------------------------------- + : IF IMMEDIATE ' 0BRANCH , \ compile 0BRANCH HERE @ \ save location of the offset on the stack @@ -93,10 +68,6 @@ SWAP ! ; -\ BEGIN loop-part condition UNTIL -\ -- compiles to: --> loop-part condition 0BRANCH OFFSET -\ where OFFSET points back to the loop-part -\ This is like do { loop-part } while (condition) in the C language : BEGIN IMMEDIATE HERE @ \ save location on the stack ; @@ -107,20 +78,12 @@ , \ compile the offset here ; -\ BEGIN loop-part AGAIN -\ -- compiles to: --> loop-part BRANCH OFFSET -\ where OFFSET points back to the loop-part -\ In other words, an infinite loop which can only be returned from with EXIT : AGAIN IMMEDIATE ' BRANCH , \ compile BRANCH HERE @ - \ calculate the offset back , \ compile the offset here ; -\ BEGIN condition WHILE loop-part REPEAT -\ -- compiles to: --> condition 0BRANCH OFFSET2 loop-part BRANCH OFFSET -\ where OFFSET points back to condition (the beginning) and OFFSET2 points to after the whole piece of code -\ So this is like a while (condition) { loop-part } loop in the C language : WHILE IMMEDIATE ' 0BRANCH , \ compile 0BRANCH HERE @ \ save location of the offset2 on the stack @@ -136,23 +99,27 @@ SWAP ! \ and back-fill it in the original location ; -\ UNLESS is the same as IF but the test is reversed. -\ -\ Note the use of [COMPILE]: Since IF is IMMEDIATE we don't want it to be executed while UNLESS -\ is compiling, but while UNLESS is running (which happens to be when whatever word using UNLESS is -\ being compiled -- whew!). So we use [COMPILE] to reverse the effect of marking IF as immediate. -\ This trick is generally used when we want to write our own control words without having to -\ implement them all in terms of the primitives 0BRANCH and BRANCH, but instead reusing simpler -\ control words like (in this instance) IF. : UNLESS IMMEDIATE ' NOT , \ compile NOT (to reverse the test) [COMPILE] IF \ continue by calling the normal IF ; -\ COMMENTS ---------------------------------------------------------------------- -\ -\ FORTH allows ( ... ) as comments within function definitions. This works by having an IMMEDIATE -\ word called ( which just drops input characters until it hits the corresponding ). +: DO IMMEDIATE + ' >R , ' >R , + HERE @ +; + +: LOOP IMMEDIATE + ' R> , ' R> , ' 1+ , ' 2DUP , ' - , + ' SWAP , ' >R , ' SWAP , ' >R , + ' 0<= , ' 0BRANCH , + HERE @ - , + ' RDROP , ' RDROP , +; + + +\ COMMENTS ---------------------------------------------------------------------- + : ( IMMEDIATE 1 \ allowed nested parens by keeping track of depth BEGIN @@ -169,20 +136,6 @@ DROP \ drop the depth counter ; -( - From now on we can use ( ... ) for comments. - - STACK NOTATION ---------------------------------------------------------------------- - - In FORTH style we can also use ( ... -- ... ) to show the effects that a word has on the - parameter stack. For example: - - ( n -- ) means that the word consumes an integer (n) from the parameter stack. - ( b a -- c ) means that the word uses two integers (a and b, where a is at the top of stack) - and returns a single integer (c). - ( -- ) means the word has no effect on the stack -) - ( Some more complicated stack examples, showing the stack notation. ) : NIP ( x y -- y ) SWAP DROP ; : TUCK ( x y -- y x y ) DUP ROT ; @@ -207,34 +160,14 @@ : DECIMAL ( -- ) 10 BASE ! ; : HEX ( -- ) 16 BASE ! ; -( - PRINTING NUMBERS ---------------------------------------------------------------------- - - The standard FORTH word . (DOT) is very important. It takes the number at the top - of the stack and prints it out. However first I'm going to implement some lower-level - FORTH words: - - U.R ( u width -- ) which prints an unsigned number, padded to a certain width - U. ( u -- ) which prints an unsigned number - .R ( n width -- ) which prints a signed number, padded to a certain width. - - For example: - -123 6 .R - will print out these characters: - - 1 2 3 - - In other words, the number padded left to a certain number of characters. - - The full number is printed even if it is wider than width, and this is what allows us to - define the ordinary functions U. and . (we just set width to zero knowing that the full - number will be printed anyway). - - Another wrinkle of . and friends is that they obey the current base in the variable BASE. - BASE can be anything in the range 2 to 36. +( Compute absolute value. ) +: ABS ( n -- m) + dup 0< if + negate + then +; - While we're defining . &c we can also define .S which is a useful debugging tool. This - word prints the current stack (non-destructively) from top to bottom. -) +( PRINTING NUMBERS ---------------------------------------------------------------------- ) ( This is the underlying recursive definition of U. ) : U. ( u -- ) @@ -254,4 +187,91 @@ EMIT ; +( This word returns the width (in characters) of an unsigned number in the current base ) +: UWIDTH ( u -- width ) + BASE @ / ( rem quot ) + ?DUP IF ( if quotient <> 0 then ) + RECURSE 1+ ( return 1+recursive call ) + ELSE + 1 ( return 1 ) + THEN +; + +: U.R ( u width -- ) + SWAP ( width u ) + DUP ( width u u ) + UWIDTH ( width u uwidth ) + -ROT ( u uwidth width ) + SWAP - ( u width-uwidth ) + ( At this point if the requested width is narrower, we'll have a negative number on the stack. + Otherwise the number on the stack is the number of spaces to print. But SPACES won't print + a negative number of spaces anyway, so it's now safe to call SPACES ... ) + SPACES + ( ... and then call the underlying implementation of U. ) + U. +; + +: .R ( n width -- ) + SWAP ( width n ) + DUP 0< IF + NEGATE ( width u ) + 1 ( save a flag to remember that it was negative | width n 1 ) + ROT ( 1 width u ) + SWAP ( 1 u width ) + 1- ( 1 u width-1 ) + ELSE + 0 ( width u 0 ) + ROT ( 0 width u ) + SWAP ( 0 u width ) + THEN + SWAP ( flag width u ) + DUP ( flag width u u ) + UWIDTH ( flag width u uwidth ) + -ROT ( flag u uwidth width ) + SWAP - ( flag u width-uwidth ) + + SPACES ( flag u ) + SWAP ( u flag ) + + IF ( was it negative? print the - character ) + '-' EMIT + THEN + + U. +; + +: U. U. SPACE ; + +: . 0 .R SPACE ; + +: .S ( -- ) + '<' EMIT DEPTH U. '>' EMIT SPACE + PSP0 @ 1+ + BEGIN + DUP PSP@ 2 - <= + WHILE + DUP @ . + 1+ + REPEAT + DROP +; + +( ? fetches the integer at an address and prints it. ) +: ? ( addr -- ) @ . ; + +( c a b WITHIN returns true if a <= c and c < b ) +: WITHIN + ROT ( b c a ) + OVER ( b c a c ) + <= IF + > IF ( b c -- ) + TRUE + ELSE + FALSE + THEN + ELSE + 2DROP ( b c -- ) + FALSE + THEN +;