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From: pepke@gw.scri.fsu.edu (Eric Pepke)
Newsgroups: comp.sys.mac.programmer
Subject: Re: From Pascal to C without a hitch ?
Message-ID: <1158@sun13.scri.fsu.edu>
Date: 17 Oct 90 20:48:56 GMT
Sender: news@sun13.scri.fsu.edu
Organization: Florida State University, but I don't speak for them
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References:<1990Oct17.151226.2449@fennel.cc.uwa.oz.au>

Pascal and C are almost identical.  This no doubt explains why the flame 
wars over which is "better" and why are so bitter and vitriolic.  Nothing 
starts a holy war like a tiny difference in interpretation of doctrine.

They are almost identical because they started off nearly so, as 
ALGOL-type block-structured procedural languages.  Also, over the years, 
people have been working to put C-like features such as loop breaks and 
type casts into PASCAL and PASCAL-like features such as strong typing in 
functions into C.  The remaining differences tend to be mostly syntactic 
or obscure and avoidable.

It is too bad you haven't yet had languages like APL, SNOBOL, PROLOG, and 
LISP, which would help you appreciate just how really small the difference 
is.  But you can still get the same result by thinking about BASIC all the 
time.

The following is a list of about 90% of the real differences between 
PASCAL and C.  In most cases there's, near enough, a one-to-one 
correspondence, in others there is quite a bit of difference in the 
details.  Warning!  The mere possesion of such a list can still get you 
burned as a heretic in many parts of the world.  On the other hand, it 
might help you get your job done.  This list, plus a copy of Kernhigan &
Ritchie, should enable you to convert sample programs from PASCAL to C, and 
after a few tries, you will know C.

Pascal                                C
------                                -
BEGIN ... END                         { ... }
IF foo THEN bar [ ELSE moo ]          IF (foo) bar; [ ELSE moo ]
; between statements                  ; at end of statement
:=                                    =
=                                     ==
<>                                    !=
NOT                                   !
PROGRAM ... END .                     main() { ... }
RECORD                                struct
variant RECORD                        union
REAL                                  float, double
INTEGER                               short, long, int
WHILE foo DO bar                      while (foo) bar
REPEAT foo UNTIL bar                  do { foo } while (!bar)
bork;  (proc or function call)        bork();
FUNCTION toad : type;                 type toad()
  toad := 3;                            return 3;
CASE foo of                           switch (foo)
  1:                                    case 1:   (remember break at end)
ARRAY glop[0..9] of integer           int glop[10]
TYPE section                          typedef
foo . bar                             foo . bar
foo ^. bar                            foo -> bar
foo^                                  *foo
WITH                                  no such animal
OTHERWISE    (nonstandard)            default:
declared, numeric labels              undeclared, nonnumeric labels
FOR k := 0 TO 9 DO bork               for (k = 0; k < 10; ++k) bork
CYCLE        (nonstandard)            continue
LEAVE        (nonstandard)            break
a AND b  (a and b evaluated first)    a && b  (b only evaluated if a)
a OR b   (a and b evaluated first)    a || b  (b only evaluated if not a)
nested procedures and functions       no such animal
CHAR is not a number, use ORD()       char is a number as well as a character
type(foo)    (nonstandard)            (type) foo


Eric Pepke                                    INTERNET: pepke@gw.scri.fsu.edu
Supercomputer Computations Research Institute MFENET:   pepke@fsu
Florida State University                      SPAN:     scri::pepke
Tallahassee, FL 32306-4052                    BITNET:   pepke@fsu

Disclaimer: My employers seldom even LISTEN to my opinions.
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