'''[http://www.schemers.org/%|%Scheme]''' is derivate of [Lisp].  A programming
language with even less syntax than Tcl itself. (but special forms and the
like...? [RS])



** Reference **

   [BOOK Structure and Interpretation of Computer Programs%|%Structure and Interpretation of Computer programs] , by Harold Abelson , Gerald Jay Sussman , Julie Sussman:   



** See Also **

   [Muddy Scheme]:   a Scheme implementation in [Tcl]

   [Playing Scheme]:   
   
   [Tcl and LISP]:   
   
   [Playing LISP]:   
   
   [Serial summing]:   

   [Cameron Laird%|%Cameron Laird's] [http://phaseit.net/claird/comp.lang.scheme/scheme.html%|%personal notes on Scheme]:   




** Description **

[wdb]: I strongly disagree that Scheme has less syntax than Tcl! Reason: the symbols have a value ''per se''. Tcl has no symbols as $varname is just a shortcut for [[set varname]] where ''varname'' is just a constant, and the procedure addressed by ''set'' carries all the semantics. In Tcl, the command ''list unknown'' returns ''unknown'' because it is a constant. In Scheme, ''(list unknown)'' throws an error unless a symbol ''unknown'' is defined. If you want to list an unknown symbol, indeed, you need the special form ''(quote unknown)'' resp. its shortcut '' 'unknown''. 

   * In Lisp, the special form ''quote'' is essential. 
   * In Tcl, it is not necessary as it can be defined as a regular procedure as follows:

======
proc quote x {
    set x
}
======

(Thank you, [RS], for the hint with the combinator ''Identity''!)

----

There's a [Tk]Scheme.  [[maybe more than one?]]

[wdb]: There is a Tk connection to the Scheme implementation Chicken [http://wolf-dieter-busch.de/html/Software/Tools/ChickenTk.htm].
Its successor [http://www.t3x.org/pstk/] is called '''PS/TK''' http://sourceforge.net/projects/pstk/ (maintained by Phil Bewig)
and is maintained by Nils M. Holm [http://t3x.org/nmh/].
Nils told me that PS/TK works with PLT Scheme on Win, on Scheme 48, and on Gambit.

----

One interesting difference is that setting of (only global?) variables and function definition both are done with ''define'', which creates a lambda if its first element is a list. Just for experimenting, here's how to have that in Tcl:

======
proc define {what how} {
    if {[llength $what] == 1} {
         uplevel 1 set $what [list $how]
    } else {
         proc [lindex $what 0] [lrange $what 1 end] $how
    }
}
======
======none
% define x 42
42
% define {+ x y} {expr {$x+$y}}
% + $x $x
84
======

This prevents us from having spaces in variable names (not a big problem), but presents the function name and arguments in one list, similar to how it will later be called - people sometimes wonder why we define `proc foo {x y} {..}` but call it `foo $x $y`...

<<categories>> Language | Functional Programming