4.3.3 Flonums (original) (raw)

4.3.3 Flonums🔗ℹ

The racket/flonum library provides operations likefl+ that consume and produce onlyflonums. Flonum-specific operations can provide better performance when used consistently, and they are as safe as generic operations like +.

See also Fixnum and Flonum Optimizations in The Racket Guide.

4.3.3.1 Flonum Arithmetic🔗ℹ

Like +, -, *, /, and abs, but constrained to consume flonums. The result is always aflonum.

Changed in version 7.0.0.13 of package base: Allow zero or more arguments for fl+ and fl*and one or more arguments for fl- and fl/.

Changed in version 7.0.0.13 of package base: Allow one argument, in addition to allowing two or more.

Returns a value like a, but potentially discards precision and range so that the result can be represented as a single-precision IEEE floating-point number (even if single-flonums are not supported).

Using flsingle on the arguments and results of fl+,fl-, fl*, fl/, and flsqrt—that is, performing double-precision operations on values representable in single precision and then rounding the result to single precision—is always the same as performing the corresponding single-precision operation [Roux14]. (For other operations, the IEEE floating-point specification does not make enough guarantees to say more about the interaction with flsingle.)

Added in version 7.8.0.7 of package base.

Like sin, cos, tan, asin,acos, atan, log, exp, andsqrt, but constrained to consume and produceflonums. The result is +nan.0 when a number outside the range -1.0 to 1.0 is given to flasin orflacos, or when a negative number is given to fllogor flsqrt.

Like expt, but constrained to consume and produceflonums.

Due to the result constraint, the results compared to exptdiffer in the following cases:These special cases correspond to pow in C99 [C99].

• (flexpt -1.0 +inf.0) — 1.0
• (flexpt a +inf.0) where a is negative — (expt (abs a) +inf.0)
• (flexpt a -inf.0) where a is negative — (expt (abs a) -inf.0)
• (expt -inf.0 b) where b is a non-integer:
  • b is negative — 0.0
  • b is positive — +inf.0
• (flexpt a b) where a is negative and b is not an integer — +nan.0

Like exact->inexact, but constrained to consume exact integers, so the result is always a flonum.

Equivalent to (random rand-gen).

4.3.3.2 Flonum Vectors🔗ℹ

A flvector is like a vector, but it holds only inexact real numbers. This representation can be more compact, and unsafe operations on flvectors (seeracket/unsafe/ops) can execute more efficiently than unsafe operations on vectors of inexact reals.

An f64vector as provided by ffi/vector stores the same kinds of values as a flvector, but with extra indirections that make f64vectors more convenient for working with foreign libraries. The lack of indirections makes unsafeflvector access more efficient.

Two flvectors are equal? if they have the same length, and if the values in corresponding slots of the flvectors areequal?.

A printed flvector starts with #fl(, optionally with a number between the #fl and(. See Reading Vectors for information on reading flvectors and Printing Vectors for information on printing flvectors.

Returns #t if v is a flvector, #f otherwise.

Creates a flvector containing the given inexact real numbers.

Example:

> (flvector 2.0 3.0 4.0 5.0)
(flvector 2.0 3.0 4.0 5.0)

Creates a flvector with size elements, where every slot in the flvector is filled with x.

Example:

> (make-flvector 4 3.0)
(flvector 3.0 3.0 3.0 3.0)

Returns the length of vec (i.e., the number of slots in theflvector).

Returns the inexact real number in slot pos ofvec. The first slot is position 0, and the last slot is one less than (flvector-length vec).

Sets the inexact real number in slot pos of vec. The first slot is position 0, and the last slot is one less than(flvector-length vec).

Creates a fresh flvector of size (- end start), with all of the elements of vec from start (inclusive) toend (exclusive).

Returns a sequence equivalent to vec when no optional arguments are supplied.

The optional arguments start, stop, andstep are as in in-vector.

A in-flvector application can provide better performance for flvector iteration when it appears directly in a for clause.

(for/flvector maybe-length (for-clause ...) body ...)
(for*/flvector maybe-length (for-clause ...) body ...) maybe-length = | #:length length-expr	#:length length-expr #:fill fill-expr length-expr : exact-nonnegative-integer? fill-expr : flonum?

Creates a flvector containing the given inexact real numbers. For communication among places, the new flvector is allocated in the shared memory space.

Example:

> (shared-flvector 2.0 3.0 4.0 5.0)
(flvector 2.0 3.0 4.0 5.0)

Creates a flvector with size elements, where every slot in the flvector is filled with x. For communication among places, the new flvector is allocated in the shared memory space.

Example:

> (make-shared-flvector 4 3.0)
(flvector 3.0 3.0 3.0 3.0)