Re: [TCLCORE] Prototype Implementation of TIP 672 - $(expr) Syntax

[Phillip B. <phi...@um...>]

Let me try making my previous email a little more concise since it hasn't
generated any follow-ups.

1) Is there a bust in the TIP 672 example code.  I can't run this code from
the TIP:

set {} foobar             ;# scalar variable

set (index) "array value" ;# array variable

When I run that, I get:

can't set "(index)": variable isn't array


Please explain.

2) The bash shell uses the syntax $(( expression )) for arithmetic.  Does
that syntax solve the problem of the unnamed array ambiguity that $(
expression ) introduces?  The $(( expression )) syntax, at least in my
small example, seems illegal.  I am only testing this out on a simple case
I tried after the above code didn't work:

% array set {} { 2+2 5 }

% puts $(2+2)

5


The above code illustrates the problem with $(2+2) being interpreted as an
index into the unnamed array.  If I try doing that with an extra ( in the
expression, it is invalid syntax:

% array set {} { (2+2) 5 }

% puts $((2+2))

invalid character in array index


To get at the array element named (2+2), you have to add escape characters:


% puts $(\(2+2\))

5


It seems to me that if $(( expression )) works generally, it has several
advantages:

   - it is easier to read and type than {=}{ expression }.  (While {=} adds
   only two characters, { and } are shifted, = is unshifted which makes for
   much slower typing.)
   - it has precedent in bash
   - it doesn't overload the meaning of preexisting valid syntax.

Are there other issues with $(( expression )) that I don't know of?  Please
explain?

Phil