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 23.2 Optional Arguments
 =======================
 
 Scheme procedures, as defined in R5RS, can either handle a fixed number
 of actual arguments, or a fixed number of actual arguments followed by
 arbitrarily many additional arguments.  Writing procedures of variable
 arity can be useful, but unfortunately, the syntactic means for handling
 argument lists of varying length is a bit inconvenient.  It is possible
 to give names to the fixed number of argument, but the remaining
 (optional) arguments can be only referenced as a list of values (
 Lambda).
 
    Guile comes with the module `(ice-9 optargs)', which makes using
 optional arguments much more convenient.  In addition, this module
 provides syntax for handling keywords in argument lists (
 Keywords).
 
    Before using any of the procedures or macros defined in this section,
 you have to load the module `(ice-9 optargs)' with the statement:
 
      (use-modules (ice-9 optargs))
 

Menu

 
* let-optional Reference      Locally binding optional arguments.
* let-keywords Reference      Locally binding keywords arguments.
* lambda* Reference           Creating advanced argument handling procedures.
* define* Reference           Defining procedures and macros.
 

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