teal.code (version 0.6.0)

eval_code: Evaluate code in qenv

Description

Evaluate code in qenv

Usage

eval_code(object, code)
# S3 method for qenv
within(data, expr, ...)

Value

qenv environment with code/expr evaluated or qenv.error if evaluation fails.

Arguments

object

(qenv)

code

(character, language or expression) code to evaluate. It is possible to preserve original formatting of the code by providing a character or an expression being a result of parse(keep.source = TRUE).

data

(qenv)

expr

(expression) to evaluate. Must be inline code, see Using language objects...

...

named argument value will substitute a symbol in the expr matched by the name. For practical usage see Examples section below.

Using language objects with <code>within</code>

Passing language objects to expr is generally not intended but can be achieved with do.call. Only single expressions will work and substitution is not available. See examples.

Details

eval_code() evaluates given code in the qenv environment and appends it to the code slot. Thus, if the qenv had been instantiated empty, contents of the environment are always a result of the stored code.

within() is a convenience method that wraps eval_code to provide a simplified way of passing expression. within accepts only inline expressions (both simple and compound) and allows to substitute expr with ... named argument values.

Examples

# evaluate code in qenv
q <- qenv()
q <- eval_code(q, "a <- 1")
q <- eval_code(q, "b <- 2L # with comment")
q <- eval_code(q, quote(library(checkmate)))
q <- eval_code(q, expression(assert_number(a)))

# evaluate code using within
q <- qenv()
q <- within(q, {
  i <- iris
})
q <- within(q, {
  m <- mtcars
  f <- faithful
})
q
get_code(q)

# inject values into code
q <- qenv()
q <- within(q, i <- iris)
within(q, print(dim(subset(i, Species == "virginica"))))
within(q, print(dim(subset(i, Species == species)))) # fails
within(q, print(dim(subset(i, Species == species))), species = "versicolor")
species_external <- "versicolor"
within(q, print(dim(subset(i, Species == species))), species = species_external)

# pass language objects
expr <- expression(i <- iris, m <- mtcars)
within(q, expr) # fails
do.call(within, list(q, expr))

exprlist <- list(expression(i <- iris), expression(m <- mtcars))
within(q, exprlist) # fails
do.call(within, list(q, do.call(c, exprlist)))