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Re: how far does eval go when module gets compiled?

From: Taylan Ulrich Bayırlı/Kammer
Subject: Re: how far does eval go when module gets compiled?
Date: Tue, 12 Jan 2016 08:56:49 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)

Matt Wette <address@hidden> writes:

> When a module is compiled to generate a .go file is it possible to know 
> (predict) what will be evaluated?
> For example
> (define-module (foo) #:export (bar))
> (define bar (+ 3 4))
> Is the “+” executed at compile time or at load time?

Nothing is really evaluated during compilation.  (Not counting
optimization like partial evaluation.)

The "top-level" of a module is evaluated once when the module is loaded
into the run-time, whether it's in source form or a compiled .go.

So the "(+ 3 4)" in your example is (theoretically) evaluated when some
piece of code containing e.g. (use-modules (foo)) is executed, and the
module was not already loaded into the running Guile process.  (Although
due to optimization, that "(+ 3 4)" will probably be turned into 7 at

Note that there is a macro called 'eval-when' which can let you
explicitly evaluate expressions at compile-time.

And of course, all macro procedures get evaluated at compile-time to
transform the compiled code as desired.

Hope that helps,

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