Parameter Utilities

8.12

Parameter Utilities🔗ℹ

by Dave Herman and Sam Tobin-Hochstadt.

This library provides several utilities for parameters.

1 Getting Started🔗ℹ

Everything in this library is exported by a single module:

(require parameter)

package: parameter

2 Pseudo-Parameters🔗ℹ

A pseudo-parameter is like a Racket parameter, but comprises both an accessor and a mutator function. This can be used, for example, to create compound parameters that simultaneously update multiple parameters.

procedure
(make-pseudo-parameter getter setter) → (pseudo-parameter/c a)
getter : (-> a)
setter : (a -> any)

Constructs a new pseudo-parameter with getter and setter functions.

procedure
(pseudo-parameter? x) → boolean?
x : any

Determines whether a given value is a pseudo-parameter.

procedure
(pseudo-parameter/c c) → contract?
c : contract?

A contract constructor for pseudo-parameters with an underlying value of contract c.

3 Parameter Sets🔗ℹ

A parameter set is a collection of Racket parameters that can be read or written to all at once with a prefab structure. Because the structure is prefab, a parameter set can also easily be marshalled and demarshalled (assuming its values are all writeable, of course).

syntax
(define-parameter-set struct-id pseudo-id
(param-id default-expr maybe-guard) ...)

maybe-guard =
| guard-expr

Defines a parameter set. The struct-id is defined as a prefab structure type with one field for each parameter in the set, in declaration order. The pseudo-id is defined as a pseudo-parameter that reads or writes the values of all the parameters in the set simultaneously. Each param-id is defined as a parameter with default value computed by default-expr and optional guard computed by maybe-guard.