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mirror of https://github.com/hsoft/collapseos.git synced 2024-12-24 14:18:06 +11:00

Add CASE..OF words

This commit is contained in:
Virgil Dupras 2020-04-16 15:07:31 -04:00
parent 733aff7b7a
commit 5067d40e3b
5 changed files with 57 additions and 28 deletions

18
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@ -5,12 +5,12 @@ definitions. In the INTERPRET loop, they don't have the desired
effect because each word from the input stream is executed
immediately. In this context, branching doesn't work.
(br) -- Branches by the number specified in the 2 following
bytes. Can be negative.
(?br) f -- Branch if f is false.
( -- *I* Comment. Ignore rest of line until ")" is read.
[ -- Begin interpretative mode. In a definition, words
between here and "]" will be executed instead of
compiled.
] -- End interpretative mode.
ABORT -- Resets PS and RS and returns to interpreter. (cont.)
f IF A ELSE B THEN: if f is true, execute A, if false, execute
B. ELSE is optional.
BEGIN .. f UNTIL: if f is false, branch to BEGIN.
BEGIN .. AGAIN: Always branch to BEGIN.
x y DO .. LOOP: LOOP increments y. if y != x, branch to DO.
x CASE y OF A ENDOF z OF B ENDOF C ENDCASE: If x == y, execute
A, if x == z, execute B. Otherwise, execute C.
(cont.)

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@ -1,16 +1,15 @@
(cont.)
ABORT" x" -- *I* Compiles a ." followed by a ABORT.
AGAIN I:a -- *I* Jump backwards to preceeding BEGIN.
BEGIN -- I:a *I* Marker for backward branching with
AGAIN.
ELSE I:a -- *I* Compiles a (fbr) and set branching
cell at a.
EXECUTE a -- Execute wordref at addr a
IF -- I:a *I* Compiles a (fbr?) and pushes its
cell's addr
INTERPRET -- Get a line from stdin, compile it in tmp
memory, then execute the compiled
contents.
QUIT R:drop -- Return to interpreter prompt immediately
RECURSE R:I -- R:I-2 Run the current word again.
THEN I:a -- *I* Set branching cell at a. (cont.)
(br) -- Branches by the number specified in the 2
following bytes. Can be negative.
(?br) f -- Branch if f is false.
( -- *I* Comment. Ignore input until ")" is read.
[ -- Begin interpretative mode. In a definition,
execute words instead of compiling them.
] -- End interpretative mode.
ABORT -- Resets PS and RS and returns to interpreter.
ABORT" x" -- *I* Compiles a ." followed by a ABORT.
EXECUTE a -- Execute wordref at addr a
INTERPRET -- Get a line from stdin, compile it in tmp memory,
then execute the compiled contents.
QUIT -- Return to interpreter prompt immediately
EXIT! -- Exit current INTERPRET loop.

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@ -1,4 +0,0 @@
(cont.)
UNTIL f -- *I* Jump backwards to BEGIN if f is
false.
EXIT! -- Exit current INTERPRET loop.

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@ -55,6 +55,27 @@
H@ 2- ( push a. -2 for allot offset )
; IMMEDIATE
( During a CASE, the stack grows by 1 at each ENDOF so that
we can fill all those ENDOF branching addrs. So that we
know when to stop, we put a 0 on PSP. That's our stopgap. )
: CASE 0 ; IMMEDIATE
: OF
COMPILE OVER COMPILE =
[COMPILE] IF
; IMMEDIATE
: ENDOF [COMPILE] ELSE ; IMMEDIATE
( At this point, we have something like "0 e1 e2 e3 val". We
want top drop val, and then call THEN as long as we don't
hit 0. )
: ENDCASE
BEGIN
DUP NOT IF DROP EXIT THEN
[COMPILE] THEN
AGAIN
COMPILE DROP
; IMMEDIATE
: CREATE
(entry) ( empty header with name )
11 ( 11 == cellWord )

13
tests/forth/test_flow.fs Normal file
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@ -0,0 +1,13 @@
: foo
CASE
'X' OF 42 ENDOF
0x12 OF 43 ENDOF
255 OF 44 ENDOF
45
ENDCASE
;
'X' foo 42 #eq
0x12 foo 43 #eq
255 foo 44 #eq
254 foo 45 #eq