How do I get the type of a value in Scheme?

Question

I want a function that gets the type of a value at runtime. Example use:

(get-type a)

where a has been defined t

Answer 1

In Scheme implementations with a Tiny-CLOS-like object system, you can just use class-of. Here's a sample session in Racket, using Swindle:

$ racket -I swindle
Welcome to Racket v5.2.1.
-> (class-of 42)
#
-> (class-of #t)
#
-> (class-of 'foo)
#
-> (class-of "bar")
#

And similarly with Guile using GOOPS:

scheme@(guile-user)> ,use (oop goops)
scheme@(guile-user)> (class-of 42)
$1 = #<  14d6a50>
scheme@(guile-user)> (class-of #t)
$2 = #<  14c0000>
scheme@(guile-user)> (class-of 'foo)
$3 = #<  14d3a50>
scheme@(guile-user)> (class-of "bar")
$4 = #<  14d3b40>