[R-gregmisc-users] SF.net SVN: r-gregmisc: [1115] trunk/SASxport

[<wa...@us...>]

Revision: 1115
          http://r-gregmisc.svn.sourceforge.net/r-gregmisc/?rev=1115&view=rev
Author:   warnes
Date:     2007-08-02 18:44:23 -0700 (Thu, 02 Aug 2007)

Log Message:
-----------
Add "assert" function to avoid dependenct on gtools.

Added Paths:
-----------
    trunk/SASxport/R/assert.R
    trunk/SASxport/man/assert.Rd

Added: trunk/SASxport/R/assert.R
===================================================================
--- trunk/SASxport/R/assert.R	                        (rev 0)
+++ trunk/SASxport/R/assert.R	2007-08-03 01:44:23 UTC (rev 1115)
@@ -0,0 +1,6 @@
+## useful function, raises an error if the FLAG expression is FALSE
+assert <- function( FLAG )
+  {
+    if(!all(FLAG))
+      stop("Failed Assertion") 
+  }

Added: trunk/SASxport/man/assert.Rd
===================================================================
--- trunk/SASxport/man/assert.Rd	                        (rev 0)
+++ trunk/SASxport/man/assert.Rd	2007-08-03 01:44:23 UTC (rev 1115)
@@ -0,0 +1,42 @@
+\name{assert}
+\alias{assert}
+\title{Generate an error if an expression is not true.}
+\description{
+  Generate an error if an expression is not true.
+}
+\usage{
+assert(FLAG)
+}
+\arguments{
+  \item{FLAG}{ Expression that should evaluate to a boolean vector}
+}
+\details{
+  Assert generate an error if its aregument does not evaluate to 
+  boolean (vector) containing only \code{TRUE} values.  This is useful
+  for defensinve programming as it provides a mechanism for checking
+  that certain facts, the 'assertions', do in fact hold.  Checking of 
+  'assertions' is an important tool in the development of robust program
+  code.
+}
+\value{
+  None.  Evaluated only for its side effect.
+}
+\author{Gregory R. Warnes \email{wa...@bs...} }
+\seealso{ \code{\link[base]{stop}}, \code{\link[base]{warning}} }
+\examples{
+
+## Trivial example
+posSqrt <- function(x)
+  {
+    assert(x>=0)
+    sqrt(x)
+  }
+
+posSqrt(1:10) # works fine, no messages
+\dontrun{
+posSqrt(-5:5) # generates an error, since the asssertion is not met
+}
+
+
+}
+\keyword{programming}


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