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From: "Rod Pemberton" <dont_use_email@xnohavenotit.cnm>
Newsgroups: comp.lang.forth
Subject: Re: Forth reinvention
Date: Thu, 20 Feb 2014 20:42:32 -0500
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On Thu, 20 Feb 2014 18:25:04 -0500, Alex McDonald <blog@rivadpm.com> wrote:
> on 20/02/2014 21:16:16, "Rod Pemberton" wrote:
>> On Thu, 20 Feb 2014 09:56:59 -0500, Alex McDonald <blog@rivadpm.com>

>> Of course, in C the syntax uses braces, if the block is more
>> than just one statement:
>>
>> [snip]
>
> This is legal C that has no blocks.
>
>   if ( x==y ) then a=1; else b=1;
>

Sorry, it's not legal C.  C has no "then" ...  :-)

Did you catch that after you posted and cringe?  ;-)

So, your example, fixed:

   if ( x==y ) a=1; else b=1;

That example does too have blocks.  They just don't need to
be marked.  I mentioned that above:

RP> "if the block is more than just one statement"

Those blocks are only one statement.

The fixed example is the same as this:

if(x==y)
   a=1;
else
   b=1;

which is the same as this:

/* braces optional */
/* indicates location of the block */

if(x==y)
{
   a=1;
}
else
{
   b=1;
}

You only need the braces for more than one statement per block:

/* braces required */

if(x==y)
{
   a=1;
   c=2;
}
else
{
   b=1;
   d=3;
}

Of course, most "skilled" C programmers prefer to format C (oddly)
like so:

/* with spaces, offset braces */

if ( x == y ) {
   a = 1;
   c = 2;
}
else {
   b = 1;
   d = 3;
}

The problem with that is it leads to misaligned braces and/or
indentation over time.

And, of course, in C, you can write that without any formatting
or spacing at all:

if(x==y){a=1;c=2;}else{b=1;d=3;}

But, you (generally) need a space here, although it's not required:

if(x==y)a=1;else b=1;

That space depends on the parsing implementation.  Most C parsers need it.
Otherwise, IIRC, the only place C requires a space is for "long long".   
Other
C types are just one word, not including sign: "int" "short" "long" "char".

>> These locations
>> correspond to where they are used in Forth control-flow words too.
>> Some Forths use BRANCH and 0BRANCH or ?BRANCH to place these branches.
>> The keywords in C mark some of other locations just as in Forth. The
>> rest are escape control-flow words like UNLOOP and EXIT in Forth or
>> 'break', 'continue' or 'goto' in C.
>>
>> Block
>> http://en.wikipedia.org/wiki/Block_(programming)
>>
>> Control-flow
>> http://en.wikipedia.org/wiki/Control_flow
>
> Control flow doesn't make it a block structured language (and the
> articles you provide make that clear).
>

I don't know what you're replying to here.  You seem to be conflating
control flow with block structured languages.  Then, you're ascribing
it to me ...

> { int a; a=1; f(a) } { int b; b=2; f(b) }
>
> and not a control flow in sight.
>

C has blocks.  Blocks aren't marked by keywords.  They're marked by
braces.  C's not a block structured language.

Forth has blocks.  Blocks are marked by keywords.  Forth is a block
structured language.  Those keywords correspond to control flow.

Even if we throw C's procedures and Forth's colon-definition into
the mix, I don't see that anything changes.  Those mark blocks too.


Rod Pemberton