[Caml-list] getting the value of the first expression

[Caml-list] getting the value of the first expression

[Rafael 'Dido' Sevilla]

I'm trying to write a simple compiler using Objective Caml, and what I
can say is that it's been a far more pleasant experience than doing the
same thing in C and Yacc, and I've learned a fair bit of the language
this way.  However there's one small thing I've wanted to do because
it's needed in my compiler.  Say I have a group of functions like this.

emit_parm "ldc" offset;
emit "ind"

The value of this whole expression is the value of the emit application.
 What if I want the value of the entire expression to be the value of
the emit_parm application?  I can't interchange the order of these two
expressions obviously because the two function applications have side
effects (they generate the assembly language for my virtual machine
architecture) Is there a way to do this?  I've been able to work around
my ignorance of the existence of such a feature but I can't help but
feel that there *must* be a better way.

One way I've thought of is to create a reference, but I can't help but
feel that there's another way to do it.

-- 
Rafael R. Sevilla <sevillar@team.ph.inter.net>   +63(2)   8177746 ext. 8311
Programmer, Inter.Net Philippines                +63(917) 4458925
http://dido.engr.internet.org.ph/                OpenPGP Key ID: 0x5CDA17D8
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Re: [Caml-list] getting the value of the first expression

[Markus Mottl]

On Thu, 18 Oct 2001, Rafael 'Dido' Sevilla wrote:
> emit_parm "ldc" offset;
> emit "ind"

If you want to return the result of "emit_parm", just bind it:

  let res = emit_parm "ldc" offset in
  emit "ind";
  res

Regards,
Markus Mottl

-- 
Markus Mottl                                             markus@oefai.at
Austrian Research Institute
for Artificial Intelligence                  http://www.oefai.at/~markus
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Re: [Caml-list] getting the value of the first expression

[Dmitry Lomov]

Hi Rafael, 
On Thu, 18 Oct 2001, Rafael 'Dido' Sevilla wrote:

> it's needed in my compiler.  Say I have a group of functions like this.
> 
> emit_parm "ldc" offset;
> emit "ind"
> 
> The value of this whole expression is the value of the emit application.
>  What if I want the value of the entire expression to be the value of
> the emit_parm application?  I can't interchange the order of these two
> expressions obviously because the two function applications have side
> effects (they generate the assembly language for my virtual machine
> architecture) Is there a way to do this?  I've been able to work around
> my ignorance of the existence of such a feature but I can't help but
> feel that there *must* be a better way.

The better way is:

let value = emit_parm "ldc" offset in
emit "ind"; value

Dmitry
-- 
Dmitry Lomov / Lanit-TERCOM Inc.
Phone: +7(812)428-45-24
e-mail: dsl@tepkom.ru

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Re: [Caml-list] getting the value of the first expression

[Bruce Hoult]

At 5:44 PM +0800 18/10/01, Rafael 'Dido' Sevilla wrote:
>emit_parm "ldc" offset;
>emit "ind"
>
>The value of this whole expression is the value of the emit application.
>  What if I want the value of the entire expression to be the value of
>the emit_parm application?  I can't interchange the order of these two
>expressions obviously because the two function applications have side
>effects

You just need a variable binding:

   let result = emit_parm "ldc" offset in
      emit "ind";
      result

-- Bruce
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Re: [Caml-list] getting the value of the first expression

[Julian Assange]

> emit_parm "ldc" offset;
> emit "ind"
> 
> The value of this whole expression is the value of the emit application.
>  What if I want the value of the entire expression to be the value of
> the emit_parm application?  I can't interchange the order of these two

let x = emit_parm "ldc" offset
in
  emit "ind"; x

--
 Julian Assange        |If you want to build a ship, don't drum up people
                       |together to collect wood or assign them tasks and
 proff@iq.org          |work, but rather teach them to long for the endless
 proff@gnu.ai.mit.edu  |immensity of the sea. -- Antoine de Saint Exupery
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