catch_err: Simplified error handling

In galacticpolymath/GPpub: Galactic Polymath Lesson Publishing Tools

Simplified error handling

Description

Evaluate expression, returning F if it catches an error. Will downgrade error to warning. FYI, the expression is expected to do something to some other environmental variable; i.e. the result will not be the result of the expression.

Usage

catch_err(
  expr,
  keep_results = FALSE,
  add_values = NULL,
  try_harder = FALSE,
  waits = c(0.1, 0.5, 1, 2, 5)
)

Arguments

expr	the expression to be evaluated
keep_results	Affects output. See returns. default=FALSE
add_values	This will concatenate named values to output. Only works for keep_results==TRUE. Default=NULL.
try_harder	logical; do you want to iteratively try this expression after waiting an increasing amount of time(s) set by waits? default=F
waits	time(s) in seconds to wait before trying the expr again; default 5 increasing wait periods= c(0.1,0.5,1,2,5)

Details

Don't use this if you want the expression to stop on an error!

Value

• if keep_results=F, output is logical. TRUE= no error; FALSE= error.

• if keep_results=T, output is a list with success (T/F), the expression called, result (expression result), and any add_values

Examples

## Not run: 
(b<-nonExistentVariable/3)
#error
(b<-catch_err(nonExistentVariable/3))

## End(Not run)
#Result is false b/c there was an error, but error is now warning

existentVariable<-6
(d<-catch_err(existentVariable/3)) #succeeded, but result of operation lost
(f<-catch_err(existentVariable/3,keep_results=TRUE)) #now we get success & operation result

#Suppose we want to pass on some relevant info
(g<-catch_err(existentVariable/18,
              keep_results=TRUE,
              add_values=c(curr_envir=environment(),user="Matt")))

#Now, suppose we have a function that fails for mysterious reasons and want to retry after a time
#set up function that will cause an error for x number of seconds
## Not run: 
delay_success <- function(curr_time,delay_seconds){
if(Sys.time()<curr_time+delay_seconds){
  stop()
  }else{
  message("No error after 2 seconds")
  }
}

#This should succeed after several retries and 2 seconds have elapsed
tm<-Sys.time(); catch_err(delay_success(curr_time=tm,delay_seconds=2),try_harder=TRUE)

## End(Not run)

galacticpolymath/GPpub documentation built on April 5, 2025, 6:04 p.m.