withVisible Return both a Value and its Visibility

Description

This function evaluates an expression, returning it in a two element list containing its value and a flag showing whether it would automatically print.

Usage

withVisible(x)

Arguments

x	an expression to be evaluated.

Details

The argument, not an expression object, rather an (unevaluated function) call, is evaluated in the caller's context.

This is a primitive function.

Value

value	The value of x after evaluation.
visible	logical; whether the value would auto-print.

See Also

invisible, eval; withAutoprint() calls source() which itself uses withVisible() in order to correctly “auto print”.

Examples

x <- 1
withVisible(x <- 1) # *$visible is FALSE
x
withVisible(x)      # *$visible is TRUE

# Wrap the call in evalq() for special handling

df <- data.frame(a = 1:5, b = 1:5)
evalq(withVisible(a + b), envir = df)