check whether 2 R programs are identical

Question

Recently I learned that I can use identical or all.equal to check whether 2 data sets are identical.

Can I also use them to check whether 2 R programs are identical? Is there a better or more appropriate way than below?

program.1 <- readLines("c:/r stuff/test program 1.r")
program.2 <- readLines("c:/r stuff/test program 2.r")

identical(program.1, program.2)
all.equal(program.1, program.2)
isTRUE(all.equal(program.1, program.2))

Thank you for any thoughts or advice.

Here are the contents of the 2 test programs being compared:

a <- matrix(2, nrow=3, ncol=4)

b <- c(1,2,3,4,5,6,7,8,6,5,4,3,2)

table(b)

c <- runif(2,0,1)

a * b

# March 2012 Edit begins here #

Here is a small example program for which Josh's function below returns FALSE while identical and all.equal return TRUE. I name the two program files 'testa.r' and 'testb.r'.

set.seed(123)

y <- rep(NA, 10)

s <- matrix(ceiling(runif(10,0,100)), nrow=10, byrow=T)

a   <- 25
ab  <- 50
abc <- 75

for(i in 1:10) {
     if(s[i] >  a  & s[i] <= ab ) y[i] = 1
     if(s[i] >  ab & s[i] <= abc) y[i] = 2
}

s
y

Here is the R program I use to read the two files containing the above code.

program.1 <- readLines("c:/users/Mark W Miller/simple R programs/testa.r")

program.2 <- readLines("c:/users/Mark W Miller/simple R programs/testb.r")


identical(program.1, program.2)
all.equal(program.1, program.2)
isTRUE(all.equal(program.1, program.2))


parseToSame <- function(file1, file2) {
    a <- parse(file = file1)
    b <- parse(file = file2)
    attributes(a) <- NULL
    attributes(b) <- NULL
    identical(a,b)
}

parseToSame(

     "c:/users/Mark W Miller/simple R programs/testa.r",
     "c:/users/Mark W Miller/simple R programs/testb.r"

)

Answer 1

Here is a function that might be slightly more useful, in that it tests whether the two files parse to the same expression tree. (It will thus find the code in two files to be equivalent even if they have different formatting, additional blank lines and spaces, etc., as long as they parse to the same object.)

parseToSame <- function(file1, file2) {
    a <- parse(file = file1)
    b <- parse(file = file2)
    attributes(a) <- NULL
    attributes(b) <- NULL
    identical(a,b)
}

Here's a demo of the function in action:

# Create two files with same code but different formatting
tmp1 <- tempfile()
tmp2 <- tempfile()
cat("a <- 4; b <- 11; a*b \n", file = tmp1)
cat("a<-4

     b    <-    11 
     a*b \n", file = tmp2)

# Test out the two approaches
identical(readLines(tmp1), readLines(tmp2))
# [1] FALSE
parseToSame(tmp1, tmp2)
# [1] TRUE