• break

    From albert@albert@spenarnc.xs4all.nl to comp.lang.forth on Thu Apr 2 15:27:59 2026
    From Newsgroup: comp.lang.forth

    Look at this definition of QUIT. '(ACCEPT) is an execution token
    that combines the functionality of REFILL and leaves a SRC like
    specification like (c-addr n), 1+ adds the line delimiter.
    SAVE and RESTORE of the current stream is hidden in INTERPRET :
    EPIPE signals the end of the stream

    : QUIT
    POSTPONE [
    BEGIN R0 @ RSP! '(ACCEPT) CATCH DUP EPIPE = IF BYE THEN
    THROW 1+ SET-SRC INTERPRET OK AGAIN
    ;

    With slight modification we can define `` break ''
    This is a interpreter, but doesn't destroy the return stack .
    It is good for interactive debugging.

    S[ ] OK SEE break

    : break
    BEGIN '(ACCEPT) CATCH DUP EPIPE <> WHILE THROW SET-SRC INTERPRET
    REPEAT DROP
    ;


    ------ testbr.frt -----------------
    : doit 1 2 3 .S ;
    --------------
    after compilation to testbr

    testbr
    S[ 1 2 3 ]

    Now imagine that this is an extremely hard to debug function:
    You can insert a break anywhere.
    ------ testbr.frt -----------------
    : doit 1 2 break 3 .S ;
    --------------
    E.g. you discover that the 2 has to be enhanced to 3:
    You type test1 and then 1+ ^D
    /tmp: is the directory.

    ------------------------
    /tmp: test1
    1+
    \ TYPE a control-D to signal end of input.
    S[ 1 3 3 ]/tmp:
    ------------------------

    This suggests that break is a useful factor of QUIT,
    further simplifying.
    (Although I think my QUIT is not particularly involved.)
    But somehow I fail to make it fit.

    Groetjes Albert
    --
    The Chinese government is satisfied with its military superiority over USA.
    The next 5 year plan has as primary goal to advance life expectancy
    over 80 years, like Western Europe.
    --- Synchronet 3.21f-Linux NewsLink 1.2