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commit
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@ -1,9 +1,9 @@
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Flow
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Note about flow words: flow words can only be used in
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definitions. In the INTERPRET loop, they don't have the desired
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effect because each word from the input stream is executed
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immediately. In this context, branching doesn't work.
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Note that 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
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word from the input stream is executed immediately. In this
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context, branching doesn't work.
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f IF A ELSE B THEN: if f is true, execute A, if false, execute
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B. ELSE is optional.
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@ -11,6 +11,6 @@ BEGIN .. f UNTIL: if f is false, branch to BEGIN.
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BEGIN .. AGAIN: Always branch to BEGIN.
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x y DO .. LOOP: LOOP increments y. if y != x, branch to DO.
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x CASE y OF A ENDOF z OF B ENDOF C ENDCASE: If x == y, execute
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A, if x == z, execute B. Otherwise, execute C.
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(cont.)
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A, if x == z, execute B. Otherwise, execute C. x is dropped
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in case of an OF match, *but it is kept if it reaches C*. You
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have to consume it to avoid PSP leak. (cont.)
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6
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@ -1,10 +1,10 @@
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( During a CASE, the stack grows by 1 at each ENDOF so that
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we can fill all those ENDOF branching addrs. So that we
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know when to stop, we put a 0 on PSP. That's our stopgap. )
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: CASE 0 COMPILE >R ; IMMEDIATE
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: CASE 0 ; IMMEDIATE
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: OF
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COMPILE I COMPILE =
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[COMPILE] IF
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COMPILE OVER COMPILE =
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[COMPILE] IF COMPILE DROP
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; IMMEDIATE
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: ENDOF [COMPILE] ELSE ; IMMEDIATE
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6
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@ -1,11 +1,9 @@
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( At this point, we have something like "0 e1 e2 e3 val". We
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want top drop val, and then call THEN as long as we don't
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want to drop val, and then call THEN as long as we don't
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hit 0. )
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: ENDCASE
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BEGIN
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DUP NOT IF
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DROP COMPILE R> COMPILE DROP EXIT
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THEN
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DUP NOT IF DROP EXIT THEN
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[COMPILE] THEN
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AGAIN
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; IMMEDIATE
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BIN
emul/stage0.bin
BIN
emul/stage0.bin
Binary file not shown.
@ -3,11 +3,12 @@
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'X' OF 42 ENDOF
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0x12 OF 43 ENDOF
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255 OF 44 ENDOF
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45
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1+
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ENDCASE
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;
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'X' foo 42 #eq
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0x12 foo 43 #eq
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255 foo 44 #eq
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254 foo 45 #eq
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254 foo 255 #eq
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'S S0 #eq
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