rpn: Reverse Polish Notation converter/interpreter.
In rpn: Converter and Interpreter for Reverse Polish Notation Expressions

Description Usage Arguments Details Value References Examples

View source: R/rpn.R

Expects an expression in (reverse) polish notation as a character vector and returns the expression in infix notation and the evaluated expression.

1 2	rpn(rpn.expr, reverse = TRUE, eval = TRUE, clean = TRUE, vars = list(), ops = list())

`rpn.expr`	[`character`] Character vector representing the expression to convert in (reverse) polish notation.
`reverse`	[`logical(1)`] Is `rpn.expr` in reverse polish notation or polish notation? Default is `TRUE`, i.e., reverse polish notation.
`eval`	[`logical(1)`] Shall the expression be evaluated? Default is `TRUE`.
`clean`	[`logical(1)`] Should braces be removed from `rpn.expr` before interpretation? Default is `TRUE`.
`vars`	[`list`] Named list of variables which are used in the `rpn.expr` beside constants. Default is the empty list.
`ops`	[`list`] Optional named list of operators. If non-empty, the list must be of key-value type, i.e., the key is the name of the function and the value is a list with the 1) the length of the parameter vector the corresponding function expects, 2) a logical value indicating whether the function is a binary infix operator and third the actual function to be called in case the expression is evaluated.

This is a pure R implementation.

List with the components

infix: Infix representation of rpn.expr.
value: Evaluated expression or NA if eval is set to FALSE.

Lukasiewicz, Jan (1957). Aristotle's Syllogistic from the Standpoint of Modern Formal Logic. Oxford University Press.

# simple example
r = c("4", "6", "*", "6", "+")
rpn(r)
rpn(r, eval = FALSE)

# the same example but with a variable
r = c("x", "6", "*", "6", "+")
rpn(r, eval = TRUE, vars = list(x = 4))
rpn(r, eval = FALSE)

# now a more complex expression with variables and custom operators/functions
rpe = c("x", "5", "6.4", "mysum", "5", "mystuff")
mysum = function(x, y, z) x + y + z # arity 3 and no infix operation
mystuff = function(x, y) 2 * (x + y) # arity 2 and no infix operation
ops = list(mysum = list(3, FALSE, mysum), mystuff = list(2, FALSE, mystuff))
vars = list(x = 3.6)
res = rpn(rpe, ops = ops, vars = vars)