replace: replace call object Replacement

In TobCap/walkast: Walking Abstruct Syntax Tree of R

Description

replace call object Replacement

Usage

replace(before, after)

nest_expr(expr, target, count)

Arguments

before	a language object or literal
after	a language object or literal
expr	a language object
target	a langage object that you want to replace
count	count of iteration

Examples

walk_ast(quote(x + y + z), replace(quote(y), quote(www)))
walk_ast(quote(x + x + x), replace(quote(x + x), quote(x)))

# because `y + x + x` is parsed as `((y + x) + x)`,
# the next code manipulates nothing
walk_ast(quote(y + x + x), replace(quote(x + x), quote(x)))

walk_ast(quote(1 + 2 + x ^ 3), replace(quote(x), quote(y)))
walk_ast(quote(1 + 2 + x ^ 3), replace(quote(x^3), quote(y)))
walk_ast(quote(1 + 2 + x ^ 3), replace(quote(2), quote(99)))
walk_ast(quote(1 + 2 + x ^ 3), replace(quote(1+2), quote(99)))
walk_ast(quote(1 + 2 + x ^ 3), replace(quote(`+`), quote(`-`)))

nest_expr(quote((1 + x)^2), quote(x), 3)
nest_expr(quote((1 + x)^2), quote(1 + x), 3)
eval(nest_expr(quote(1 + 1 / x), quote(x), 40), list(x = 1)) == (1 + sqrt(5)) / 2

TobCap/walkast documentation built on May 9, 2019, 4:51 p.m.