gestalt

0.2.0

Breaking changes

• Formal arguments of partial(..f, ...) no longer record the original default values of ..f (since a default-value expression may reference an argument that is fixed, and therefore dropped, by partial()). Nevertheless, any default values of ..f not overridden by partial() remain in force when the function partial(..f, ...) is called.

• partial(..f, ...) can still fix arguments that match the ... argument of ..f (if present), but only when such arguments are specified by name.

Bug fix

• Default argument values of a composite function are now evaluated in the evaluation environment of the initial function. Essentially, a call like compose(f, g)(x, y, ...) is now equivalent to a call like (function(...) g(f(...)))(x, y, ...). (Previously, the initial function was called with a complete set of formal arguments, which in cases where formal arguments are mutated or mutually referenced (e.g., in the formals of base::objects()), could lead the initial function to wrongly determine the “missingness” of an argument or wrongly evaluate an argument’s default value.) As before, the signature of compose(f, ...) inherits the signature of f.

0.1.9

Gestalt now depends on a stable release of rlang, version 1.0.0 and above. (A minor internal fix was made to address a change in the behavior of rlang::is_expression().) There are no user-facing changes.

0.1.8

• The environment of a partial function expression in a %>>>% chain (e.g., the base-3 logarithm in abs %>>>% log(base = 3)) is now properly captured. Previously, it was erroneously matched to an rlang data mask, due to an internal call to rlang::eval_tidy() using positional arguments.

0.1.7

• In a %>>>% chain, a point (.) is now only matched as an argument value when it is a symbol, not a character (".") (#27).

0.1.6

This is a maintenance release to fix test failures caused by changes in the rlang package.

• The (minimum) required rlang version has been increased to 0.3.1. This version fixed a bug which prevented certain operator “sections” from being expressed. A chain like `/`(2) %>>>% sin (halve and apply sine) now works as expected.

• Formals of primitive functions now agree with those of base::args() (#18, #24). This means you can use args() to determine the names of arguments when using partial(). Thus, partial(`/`, e2 = 3) is the same as partial(`/`, , 3) is the same as division-by-3. Moreover, %>>>% chains are verified against the argument names given by args(). Thus, `/`(e2 = 2) %>>>% sin is valid, but `/`(y = 2) %>>>% sin is invalid—`/`() viewed as a closure has no argument called y.

• Support for R 3.1 has been dropped.

0.1.5

• Fixed a segfault caused by leakage of rlang internals (thanks @lionel-).

• names() now gets the names of bindings in a context (as made by let()).

0.1.4

New features

• posure() is a means of creating efficient variable (i.e., parameterized) composite functions.

  In particular, this addresses a shortcoming of the use of the magrittr %>% in functions. Instead of writing

  function(..., b = 2, n) {
    sample(...) %>% log(base = b) %>% rep(n)
  }

  which is inefficient because the function chain is created anew with each call, you can more directly curry it by writing

  posure(b = 2, n ~ {
    sample %>>>% log(base = b) %>>>% rep(n)
  })

  Not only is the posure() version more succinct, it is robuster and faster than the version with %>%, thanks to the non-standard mechanism of a closure that is “partially dynamically scoped.” (Whence the portmanteau “posure,” due to @henryaj; see the package documentation for details.)

• let() enables you to create contexts: composable local environments in which named expressions are lazily resolved in a given order. Tidyverse quasiquotation of expressions is supported, allowing you to exercise fine-grained control over the evaluation of subexpressions.

• As a companion to let(), run() evaluates an expression relative to a context. Unlike base::with(), run() supports quasiquotation and provides a means of overriding bindings in a given context.

Minor improvements

• When calling a composite function, the point (.) in an implicitly curried function may now assume any name (#10). This is useful when you want to call the argument assumed by the point by its original name, e.g., in a do.call() or lapply() invocation.

• partial() is now literally interpreted by %>>>% (#11). For instance, you you can succinctly write abs %>>>% partial(log, base = 2) instead of abs %>>>% !!partial(log, base = 2).

0.1.2

• In a composite function, default argument values following ... are no longer absorbed by ... (#6).

• Improvements to the documentation throughout.

0.1.1

• Initial release.

• fn() is extracted from nofrills 0.3.0.