A wrapped expression that can be used with operators to generate new expressions

A wrapped expression that can be used with operators to generate new expressions

delayed_expr(expr, expr_str = NULL)

Arguments

expr	an expression
expr_str	text that you want to show when this expression is printed. If NULL, the expression supplied by parameter 'expr' is used for printing.

Value

A delayed_expr object

Examples

# define a delayed expression
f_delay <- function() {
  delayed_expr(size)
}

# create a new expression
y = (1 + f_delay()) == 5

# print the unevaluated expression
y
#> [1] "((1 + size) == 5)"

if (FALSE) {
# evaluation generates an error, as size is not defined
delayed_eval(y)
}

# define size and re-evaluate
size = 0.1
delayed_eval(y)
#> [1] FALSE

# make the expression evaluate to TRUE
size = 4
delayed_eval(y)
#> [1] TRUE


# custom printing text can be added to the delayed expression
f_delay <- function() {
  delayed_expr(size, "f_delay()")
}

# create a new expression
y = (1 + f_delay()) == 5

# print with custom text
y
#> [1] "((1 + f_delay()) == 5)"