CHICKEN Scheme’s included srfi-4 module

The next mini (incomplete) guided tour through an included CHICKEN Scheme module is about (chicken srfi-4), an implementation of SRFI-4. This module provides homogeneous vectors, particularly double-precision flonum vectors (f64vectors), which can only hold flonums. In the same way (chicken flonum) is an included module for performance reasons, (chicken srfi4) provides increases performance for vectors of entries of a single type. While SRFI-4 defines ten types of homogeneous vectors:

  • unsigned integer: 8-bit (u8), 16-bit (u16), 32-bit (u32), 64-bit (u64),
  • signed integer: 8-bit (s8), 16-bit (s16), 32-bit (s32), 64-bit (s64),
  • floating-point numbers: 32-bit (f32), 64-bit (f64),

due to the use in matrico, I will only focus on the f64-typed vector.

The base functionality, as for a record (structure), is a constructor and a predicate testing for this type:

  • (make-f64vector len [val]) - Return f64vector with length-argument-many entries; optionally, all entries are set to the value argument.
  • (f64vector? any) - Return boolean answering if argument is f64vector.

To obtain the length (dimension) of the vector, similar to the non-homogeneous vector, one can use:

  • (f64vector-length vec) - Return number of entries of f64vector argument.

Similarly, the accessors follow consistently:

  • (f64vector-ref vec idx) - Return entry of f64vector argument at index argument.
  • (f64vector-set! vec idx val) - Mutate entry of f64vector argument at index argument to value argument.

Lastly, a converter from lists to f64vectors is available (again, as for the standard vector), and also the non-R5RS counterpart to subvector (from (chicken base)):

  • (list->f64vector lst) - Return f64vector from list of flonums.
  • (subf64vector vec from to) - Return f64vector holding entries of first index argument till second index argument.

Overall, this is a very natural addition of homogenous vectors to the standard vectors, even regarding extended functionality in CHICKEN. This attention to consistency and detail, is what makes CHICKEN Scheme so enjoyable. Unfortunately, some functions, like a vector-map, are neither part of this module nor SRFI-4 in general, which will be explored in the next post.