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@ -1,21 +1,11 @@
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Be sure to read "usage.txt" for a guide to Collapse OS' Forth.
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*** Glossary ***
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Stack notation: "<stack before> -- <stack after>". Rightmost is top of stack
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(TOS). For example, in "a b -- c d", b is TOS before, d is TOS after. "R:" means
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that the Return Stack is modified. "I:" prefix means "IMMEDIATE", that is, that
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this stack transformation is made at compile time.
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DOES>: Used inside a colon definition that itself uses CREATE, DOES> transforms
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that newly created word into a "does cell", that is, a regular cell ( when
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called, puts the cell's addr on PS), but right after that, it executes words
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that appear after the DOES>.
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"does cells" always allocate 4 bytes (2 for the cell, 2 for the DOES> link) and
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there is no need for ALLOT in colon definition.
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At compile time, colon definition stops processing words when reaching the
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DOES>.
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Example: ": CONSTANT CREATE HERE @ ! DOES> @ ;"
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Word references (wordref): When we say we have a "word reference", it's a
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pointer to a words *code link*. For example, the label "PLUS:" in this unit is a
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word reference. Why not refer to the beginning of the word struct? Because we
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@ -54,20 +44,6 @@ IMMEDIATE -- Flag the latest defined word as immediate.
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LITN n -- Write number n as a literal.
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VARIABLE c -- Creates cell x with 2 bytes allocation.
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Compilation vs meta-compilation. When you compile a word with "[COMPILE] foo",
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its straightforward: It writes down to HERE wither the address of the word or
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a number literal.
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When you *meta* compile, it's a bit more mind blowing. It fetches the address
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of the word specified by the caller, then writes that number as a literal,
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followed by a reference to ",".
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Example: ": foo [COMPILE] bar;" is the equivalent of ": foo bar ;" if bar is
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not an immediate. However, ": foo COMPILE bar ;" is the equivalent of
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": foo ['] bar , ;". Got it?
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Meta-compile only works with real words, not number literals.
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*** Flow ***
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Note about flow words: flow words can only be used in definitions. In the
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INTERPRET loop, they don't have the desired effect because each word from the
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@ -156,32 +132,6 @@ SLEN a -- n Push length of str at a.
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*** I/O ***
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A little word about inputs. There are two kind of inputs: direct and buffered.
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As a general rule, we read line in a buffer, then feed words in it to the
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interpreter. That's what "WORD" does. If it's at the End Of Line, it blocks and
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wait until another line is entered.
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KEY input, however, is direct. Regardless of the input buffer's state, KEY will
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return the next typed key.
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PARSING AND BOOTSTRAP: Parsing number literal is a very "core" activity of
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Forth, and therefore generally seen as having to be implemented in native code.
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However, Collapse OS' Forth supports many kinds of literals: decimal, hex, char,
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binary. This incurs a significant complexity penalty.
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What if we could implement those parsing routines in Forth? "But it's a core
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routine!" you say. Yes, but here's the deal: at its native core, only decimal
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parsing is supported. It lives in the "(parsed)" word. The interpreter's main
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loop is initially set to simply call that word.
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However, in core.fs, "(parsex)", "(parsec)" and "(parseb)" are implemented, in
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Forth, then "(parse)", which goes through them all is defined. Then, "(parsef)",
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which is the variable in which the interpreter's word pointer is set, is
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updated to that new "(parse)" word.
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This way, we have a full-featured (and extensible) parsing with a tiny native
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core.
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(parse) a -- n Parses string at a as a number and push the result
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in n as well as whether parsing was a success in f
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(false = failure, true = success)
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@ -193,11 +143,15 @@ core.
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number parsing. By default, (parse).
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(print) a -- Print string at addr a.
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. n -- Print n in its decimal form
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.X n -- Print n in its hexadecimal form. In hex, numbers
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.x n -- Print n's LSB in hex form. Always 2 characters.
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.X n -- Print n in hex form. Always 4 characters. Numbers
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are never considered negative. "-1 .X" --> ffff
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." xxx" -- *I* Compiles string literal xxx followed by a call
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to (print)
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are never considered negative. "-1 .X -> ffff"
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C< -- c Read one char from buffered input.
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DUMP n a -- Prints n bytes at addr a in a hexdump format.
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Prints in chunks of 8 bytes. Doesn't do partial
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lines. Output is designed to fit in 32 columns.
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EMIT c -- Spit char c to output stream
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IN> -- a Address of variable containing current pos in input
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buffer.
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@ -1,6 +1,6 @@
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TARGETS = runbin/runbin forth/forth
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# Those Forth source files are in a particular order
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FORTHSRCS = core.fs print.fs str.fs parse.fs readln.fs fmt.fs z80a.fs
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FORTHSRCS = core.fs cmp.fs print.fs str.fs parse.fs readln.fs fmt.fs z80a.fs
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FORTHSRC_PATHS = ${FORTHSRCS:%=../forth/%} forth/run.fs
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OBJS = emul.o libz80/libz80.o
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SLATEST = ../tools/slatest
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38
forth/cmp.fs
Normal file
38
forth/cmp.fs
Normal file
@ -0,0 +1,38 @@
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( Words useful for complex comparison operations )
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( n1 -- n1 true )
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: <>{ 1 ;
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( n1 f -- f )
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: <>} SWAP DROP ;
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: _|&
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( n1 n2 cell )
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>R >R DUP R> R> ( n1 n1 n2 cell )
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@ EXECUTE ( n1 f )
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;
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( n1 f n2 -- n1 f )
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: _|
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CREATE , DOES>
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( n1 f n2 cell )
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ROT IF 2DROP 1 EXIT THEN ( n1 true )
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_|&
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;
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: _&
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CREATE , DOES>
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( n1 f n2 cell )
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ROT NOT IF 2DROP 0 EXIT THEN ( n1 true )
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_|&
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;
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( All words below have this signature:
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n1 f n2 -- n1 f )
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' = _| |=
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' = _& &=
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' > _| |>
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' > _& &>
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' < _| |<
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' < _& &<
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64
forth/fmt.fs
64
forth/fmt.fs
@ -1,7 +1,6 @@
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( requires core, parse )
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( TODO FORGET this word )
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: PUSHDGTS
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: _
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999 SWAP ( stop indicator )
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DUP 0 = IF '0' EXIT THEN ( 0 is a special case )
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BEGIN
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@ -16,7 +15,7 @@
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( that "0 1 -" thing is because we don't parse negative
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number correctly yet. )
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DUP 0 < IF '-' EMIT 0 1 - * THEN
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PUSHDGTS
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_
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BEGIN
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DUP '9' > IF DROP EXIT THEN ( stop indicator, we're done )
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EMIT
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@ -25,24 +24,53 @@
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: ? @ . ;
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: PUSHDGTS
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999 SWAP ( stop indicator )
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DUP 0 = IF '0' EXIT THEN ( 0 is a special case )
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BEGIN
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DUP 0 = IF DROP EXIT THEN
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16 /MOD ( r q )
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SWAP ( r q )
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: _
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DUP 9 > IF 10 - 'a' +
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ELSE '0' + THEN ( q d )
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SWAP ( d q )
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AGAIN
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ELSE '0' + THEN
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;
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: .X ( n -- )
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( For hex display, there are no negatives )
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PUSHDGTS
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( For hex display, there are no negatives )
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: .x
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256 MOD ( ensure < 0x100 )
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16 /MOD ( l h )
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_ EMIT ( l )
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_ EMIT
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;
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: .X
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256 /MOD ( l h )
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.x .x
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;
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( a -- a+8 )
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: _
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DUP ( save for 2nd loop )
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':' EMIT DUP .x SPC
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4 0 DO
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DUP @
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256 /MOD SWAP
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.x .x
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SPC
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2 +
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LOOP
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DROP
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8 0 DO
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DUP C@
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DUP <>{ 0x20 &< 0x7e |> <>}
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IF DROP '.' THEN
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EMIT
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1 +
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LOOP
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LF
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;
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( n a -- )
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: DUMP
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LF
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BEGIN
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DUP 'f' > IF DROP EXIT THEN ( stop indicator, we're done )
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EMIT
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OVER 1 < IF DROP EXIT THEN
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_
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SWAP 8 - SWAP
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AGAIN
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;
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88
usage.txt
Normal file
88
usage.txt
Normal file
@ -0,0 +1,88 @@
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Collapse OS usage guide
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This document is not meant to be an introduction to Forth, but to instruct the
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user about the peculiarities of this Forth implemenation. Be sure to refer to
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dictionary.txt for a word reference.
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*** DOES>
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Used inside a colon definition that itself uses CREATE, DOES> transforms that
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newly created word into a "does cell", that is, a regular cell ( when called,
|
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puts the cell's addr on PS), but right after that, it executes words that appear
|
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after the DOES>.
|
||||
|
||||
"does cells" always allocate 4 bytes (2 for the cell, 2 for the DOES> link) and
|
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there is no need for ALLOT in colon definition.
|
||||
|
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At compile time, colon definition stops processing words when reaching the
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DOES>.
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||||
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Example: ": CONSTANT CREATE HERE @ ! DOES> @ ;"
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|
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*** Compilation vs meta-compilation
|
||||
|
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Compilation vs meta-compilation. When you compile a word with "[COMPILE] foo",
|
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its straightforward: It writes down to HERE wither the address of the word or
|
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a number literal.
|
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|
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When you *meta* compile, it's a bit more mind blowing. It fetches the address
|
||||
of the word specified by the caller, then writes that number as a literal,
|
||||
followed by a reference to ",".
|
||||
|
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Example: ": foo [COMPILE] bar;" is the equivalent of ": foo bar ;" if bar is
|
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not an immediate. However, ": foo COMPILE bar ;" is the equivalent of
|
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": foo ['] bar , ;". Got it?
|
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|
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Meta-compile only works with real words, not number literals.
|
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|
||||
*** I/O
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||||
|
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A little word about inputs. There are two kind of inputs: direct and buffered.
|
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As a general rule, we read line in a buffer, then feed words in it to the
|
||||
interpreter. That's what "WORD" does. If it's at the End Of Line, it blocks and
|
||||
wait until another line is entered.
|
||||
|
||||
KEY input, however, is direct. Regardless of the input buffer's state, KEY will
|
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return the next typed key.
|
||||
|
||||
PARSING AND BOOTSTRAP: Parsing number literal is a very "core" activity of
|
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Forth, and therefore generally seen as having to be implemented in native code.
|
||||
However, Collapse OS' Forth supports many kinds of literals: decimal, hex, char,
|
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binary. This incurs a significant complexity penalty.
|
||||
|
||||
What if we could implement those parsing routines in Forth? "But it's a core
|
||||
routine!" you say. Yes, but here's the deal: at its native core, only decimal
|
||||
parsing is supported. It lives in the "(parsed)" word. The interpreter's main
|
||||
loop is initially set to simply call that word.
|
||||
|
||||
However, in core.fs, "(parsex)", "(parsec)" and "(parseb)" are implemented, in
|
||||
Forth, then "(parse)", which goes through them all is defined. Then, "(parsef)",
|
||||
which is the variable in which the interpreter's word pointer is set, is
|
||||
updated to that new "(parse)" word.
|
||||
|
||||
This way, we have a full-featured (and extensible) parsing with a tiny native
|
||||
core.
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||||
|
||||
*** Chained comparisons
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||||
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The unit "cmp.fs" contains words to facilitate chained comparisons with a single
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reference number. This allows, for example, to easily express "a == b or a == c"
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or "a > b and a < c".
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The way those chained comparison words work is that, unlike single comparison
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operators, they don't have a "n1 n2 -- f" signature, but rather a "n1 f n2 -- n1
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f" signature. That is, each operator "carries over" the reference number in
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addition to the latest flag.
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You open a chain with "<>{" and you close a chain with "<>}". Then, in between
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those words, you can chain operators. For example, to check whether A == B or A
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== C, you would write:
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A <>{ B &= C |= <>}
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The first operator must be of the "&" type because the chain starts with its
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flag to true. For example, "<>{ <>}" yields true.
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To check whether A is in between B and C inclusively, you would write:
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A <>{ B 1 - &> C 1 + &< <>}
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