13.10 Fast-Load Serialization

The v argument must be a value that could be quoted as a literal—that is, a value without syntax objects for which (compile `',v) would work and be readable after write—or it can include correlated objects mixed with those values. The byte string produced by s-exp->fasl does not use the same format as compiled code, however.

Like (compile `',v), s-exp->fasl does not preserve graph structure, support cycles, or handle non-prefab structures. Compose s-exp->fasl with serialize to preserve graph structure, handle cyclic data, and encode serializable structures. The s-exp->fasl and fasl->s-exp functions consult current-write-relative-directory and current-load-relative-directory, respectively, in the same way as bytecode saving and loading to store paths in relative form, and they similarly allow and convert constrained srcloc values (see Printing Compiled Code).

Unless keep-mutable? is provided as true to s-exp->fasl, then mutable values in v are replaced by immutable values when the result is decoded by fasl->s-exp. Unless datum-intern? is provided as #f, then any immutable value produced by fasl->s-exp is filtered by datum-intern-literal. The defaults make the composition of s-exp->fasl and fasl->s-exp behave like the composition of write and read.

The byte-string encoding produced by s-exp->fasl is independent of the Racket version, except as future Racket versions introduce extensions that are not currently recognized. In particular, the result of s-exp->fasl will be valid as input to any future version of fasl->s-exp.

Changed in version 6.90.0.21 of package base: Made s-exp->fasl format version-independent and added the #:keep-mutable? and #:datum-intern? arguments.
Changed in version 7.3.0.7: Added support for correlated objects.