makeStack {lazy.tools}

R Documentation

Preparation of Stack

Description

Preparation of Stack

Usage

makeStack()

Details

This is a function factory which makes the following list of functions.
push, pop, inspect, length and clear

In the usual image of a stack, the newest object will be placed on top of the older objects. However, in this R version, the newest object will be placed at the end of a hidden list named valueList in the function factory environment.

It enables LIFO (Last-In First-Out) or FILO (First-In Last-Out).

Value

A list of functions
push, pop, inspect, length and clear

References

The original version is from the answer by Matt:
https://stackoverflow.com/questions/28687806 /a-better-way-to-push-and-pop-to-from-lists-in-r

Examples

 # generate functions
 stack <- makeStack()

 stack$push(3)
 stack$push(5)
 stack$push(9)
 stack$length()
 stack$inspect(1:stack$length())
 stack$pop()
 stack$inspect(1:stack$length())
 stack$pop()
 stack$inspect(1:stack$length())
 stack$pop()

 # Below causes error.
 # stack$inspect(1:stack$length())


 STACK=makeStack()
 PUSH <- STACK$push
 POP <- STACK$pop
 LEN <- STACK$length
 INSP <- STACK$inspect
 CLEAR <- STACK$clear
 PUSH( list(a=1,b=2,c="C"))
 PUSH( list(a=12,b=22,c="C2"))
 PUSH( list(a=13,b=23,c="C3"))
 INSP(1:LEN())
 POP()
 INSP(1:LEN())
 POP()
 INSP(1:LEN())

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