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(guile.info)About Expressions

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Expressions and Evaluation
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So far, we have met expressions that _do_ things, such as the `define'
expressions that create and initialize new variables, and we have also
talked about expressions that have _values_, for example the value of
the procedure invocation expression:

     (string-append "/home" "/" "andrew")

But we haven't yet been precise about what causes an expression like
this procedure invocation to be reduced to its "value", or how the
processing of such expressions relates to the execution of a Scheme
program as a whole.

This section clarifies what we mean by an expression's value, by
introducing the idea of "evaluation".  It discusses the side effects
that evaluation can have, explains how each of the various types of
Scheme expression is evaluated, and describes the behaviour and use of
the Guile REPL as a mechanism for exploring evaluation.  The section
concludes with a very brief summary of Scheme's common syntactic
expressions.

Evaluating

How a Scheme program is executed.

The REPL

Interacting with the Guile interpreter.

Syntax Summary

Common syntactic expressions -- in brief.