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Re: Add syntax highlighting to own command

• To: mathgroup at smc.vnet.net
• Subject: [mg101832] Re: Add syntax highlighting to own command
• From: earthnut at web.de (Bastian Erdnuess)
• Date: Sat, 18 Jul 2009 08:00:26 -0400 (EDT)
• References: <200907090600.CAA17547@smc.vnet.net> <h3766u$f9h$1@smc.vnet.net> <h3s24c$66k$1@smc.vnet.net>

rych <rychphd at gmail.com> wrote:

> On Jul 16, 1:19 pm, earth... at web.de (Bastian Erdnuess) wrote:
> > Bastian Erdnuess <earth... at web.de> wrote:
> 
> >
> >   Let /: ( lhs_ := Let[ vars_, expr_ /; cond_ ] ) :=
> >     Let[ vars, lhs := expr /; cond ]
> >
> 
> 
> I'm sorry, Bastian, but can I ask you what you're trying to achieve
> with these lines? Actually, I've never seen more than one SetDelayed
> in an expression.

In the help for With is written

  - You can use With[ { vars }, body /; cond ] as the right-hand side
    of a transformation rule with a condition attached.

I tried to get the same behaviour to the Let construct.

I found out one can write the upper rule also straight as

  ( lhs_ := Let[ vars_, expr_ /; cond_ ] ) ^:=
    Let[ vars, lhs := expr /; cond ]

as an UpRule.

> When I try to test this definition as follows, I get
> a "SetDelayed::shape"  error,
> 
> {x, y, z, w} :=  Let[{a = 1, b = a + 1, c = b + 1, d = a + b + c}=
> , {a,
> b, c, d}]

I don't see what you try to do.  This shouldn't match any of the rules
for Let at all.  I get the same error, also when I use a symbol like Foo
instead of Let which has no rules attached.

Bastian

• References:
  • Add syntax highlighting to own command
    • From: earthnut@web.de (Bastian Erdnuess)