### Name: stopifnot
### Title: Ensure the `Truth' of R Expressions
### Aliases: stopifnot
### Keywords: environment programming error

### ** Examples

stopifnot(1 == 1, all.equal(pi, 3.14159265), 1 < 2) # all TRUE

m <- matrix(c(1,3,3,1), 2,2)
stopifnot(m == t(m), diag(m) == rep(1,2)) # all(.) |=>  TRUE

op <- options(error = expression(NULL))
# "disable stop(.)"  << Use with CARE! >>

stopifnot(all.equal(pi, 3.141593),  2 < 2, all(1:10 < 12), "a" < "b")
stopifnot(all.equal(pi, 3.1415927), 2 < 2, all(1:10 < 12), "a" < "b")

options(op)# revert to previous error handler