[FROM MODERATOR - SORRY FOR THE DELAY IN POSTING THIS -
YAHOO HAD MARKED IT AS SPAM FOR SOME REASON]
SAMUEL A. FALVO II WROTE:
[...]
> INTERESTINGLY, BCPL DIDN'T JUST FORK OFF AND EVENTUALLY
BECOME C.
> BCPL HAS ANOTHER VARIANT, CALLED MCPL, WHICH HAS
PATTERN MATCHING.
> ALTHOUGH A STATICALLY COMPILED LANGUAGE, IT'S TYPE
SYSTEM CONSISTS OF
> CHAR AND WORD (KIND OF LIKE FORTH). MCPL WAS A
RESEARCH ATTEMPT TO
> FIND OUT IF PATTERN MATCHING COULD BE APPLIED TO
WEAKLY-TYPED
> LANGUAGES. IT WAS SUCCESSFUL INSOFAR AS IT WORKS AS A
LANGUAGE (I'VE
> DONE A WEE BIT OF CODING IN IT, AND IT WAS PRETTY
NEAT!), BUT IT
> DIDN'T GO ANYWHERE.
<OFFTOPIC>
*RUMMAGE THROUGH GOOGLE*
FOR THOSE WHO ARE INTERESTED, HERE'S THE MANUAL:
HTTP://66.102.9.104/SEARCH?Q=CACHE:IIAEY9CLNDMJ:WWW.CL.CAM.A
C.UK/~MR10/MCPLMAN.PDF&HL=EN&CT=CLNK&CD=6&GL
=UK&CLIENT=FIREFOX-A
AN HERE'S THE FIRST EXAMPLE, WHICH SHOWS SOME OF THE NEAT
FEATURES:
GET "MCPL.H"
FUN START
: => WRITEF "ENTER THREE LENGTHS: "
LET A=READN(), B=READN(), C=READN()
WRITEF("NTRIANGLE ENTERED: %D %D %D", A, B,
C)
WRITEF("NTHIS IS %S TRIANGLEN",
SORT_OF_TRIANGLE(A,B,C))
.
FUN SORT_OF_TRIANGLE
: A, B(<A), C => SORT_OF_TRIANGLE(B, A, C)
: A, B, C(<B) => SORT_OF_TRIANGLE(A, C, B)
// AT THIS POINT WE KNOW THAT A <= B <= C
: A, B, >A+B => "NOT A"
: A, ?, =A => "AN EQUALATERAL"
: A, =A, ? => "AN ISOSCELES"
: ?, =C, C => "AN ISOSCELES"
: A, B, C => C*C=A*A+B*B -> "A RIGHT
ANGLED", "A SCALENE"
.
I SUSPECT THAT THESE DAYS IT'S BEEN RATHER SUPERCEDED BY
LANGUAGES LIKE OCAML,
BUT THAT *IS* NEAT --- IT ALSO FEATURES BASIC OO SUPPORT,
EXCEPTIONS, TAGGED
DATA STRUCTURES IN PATTERNS, COROUTINES, ETC. IT LOOKS LIKE
IT WOULD BE EASY
TO COMPILE BUT QUITE HARD TO COMPILE *WELL* --- I WONDER IF
THERE ARE STILL
ANY COMPILERS AROUND? THIS MAY ACTUALLY BE USEFUL FOR
ELEGANTLY IMPLEMENTING
STATE MACHINES FOR VERY SMALL EMBEDDED PLATFORMS... THANKS
FOR POINTING IT OUT.
</OFFTOPIC>
[...]
> REALISTICALLY SPEAKING, THOUGH, PATTERN MATCHING CAN BE
RESOLVED WITH
> CAREFUL USE OF INHERITANCE. THINK ABOUT IT -- THE ONLY
REASON YOU'D
> EVER PATTERN MATCH IS TO LIST RULES DEALING WITH
EXCEPTIONAL
> CONDITIONS -- PRECISELY THE KIND OF THING POLYMORPHISM
IS DESIGNED TO
> DEAL WITH ANYWAY.
THE WAY SMALLTALK (AND PROBABLY IO, I HAVEN'T LOOKED AT IT
FOR A WHILE)
IMPLEMENT TRUE>>IFTRUE:IFFALSE: AND
FALSE>>IFTRUE:IFFALSE: IS THE CLASSIC
EXAMPLE OF THIS.
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