Eval in Haskell

[Lauri Alanko]

[We now have lost all pretence of topicality]

On Sun, Jun 01, 2003 at 08:43:03PM -0700, Ashley Yakeley wrote:
> Guile seems to be a bit "sloppy" in general. I think it just keeps a 
> dictionary of symbol bindings and passes it around at runtime.
> 
> guile> (eval '(define b 5))
> guile> b
> 5

This particular kind of sloppiness is pretty common in Scheme REPLs:

la:~$ kawa
#|kawa:1|# (eval '(define b 5))
#|kawa:2|# b
5
#|kawa:3|# 
la:~$ mzscheme
Welcome to MzScheme version 204, Copyright (c) 1995-2003 PLT
> (eval '(define b 5))
> b
5
> 
la:~$ bigloo 
------------------------------------------------------------------------------
Bigloo (2.5c)                                                            ,--^, 
`a practical Scheme compiler'                                      _ ___/ /|/  
Wed Nov 27 10:49:16 CET 2002                                   ,;'( )__, ) '   
Manuel Serrano                                                ;;  //   L__.    
email:                                                        '   \    /  '    
Manuel.Serrano@sophia.inria.fr                                     ^   ^       
------------------------------------------------------------------------------

Welcome to the interpreter

1:=> (eval '(define b 5))
b
1:=> b
5
1:=> 
la:~$ mit-scheme 
Scheme Microcode Version 14.9
MIT Scheme running under GNU/Linux
Type `^C' (control-C) followed by `H' to obtain information about interrupts.
Scheme saved on Tuesday June 18, 2002 at 2:26:05 AM
  Release 7.7.1
  Microcode 14.9
  Runtime 15.1
  SF 4.40
  Liar (Intel i386) 4.115
  Edwin 3.112

1 ]=> (eval '(define b 5) system-global-environment)

;Value: b

1 ]=> b

;Value: 5

1 ]=> 
End of input stream reached
Happy Happy Joy Joy.


... though admittedly it's a bit confusing, since "define" either binds
or assigns to a variable, depending on whether it was already bound.


Lauri Alanko
la@iki.fi