composerr_ {labelmachine}

Compose error handlers (concatenate error messages)

Description

The functions composerr(), composerr_() and composerr_parent() modify error handlers by appending character strings to the error messages of the error handling functions:

• composerr() uses non-standard evaluation.

• composerr_() is the standard evaluation alternative of composerr().

• composerr_parent() is a wrapper of composerr(), defining the parent environment as the lookup environment of the err_handler. This function looks up the prior error handling function in the parent environment of the current environment and allows you to store the modified error handling function under the same name as the error handling function from the parent environment without running into recursion issues. This is especially useful when doing error handling in nested environments (e.g. checking nested list objects) and you don not want to use different names for the error handling functions in the nested levels. If you don't have a nested environment situation, better use composerr() or composerr_().

Usage

composerr_(text_1 = NULL, err_prior = NULL, text_2 = NULL,
  sep_1 = ": ", sep_2 = ": ", env_prior = parent.frame())

composerr(text_1 = NULL, err_prior = NULL, text_2 = NULL,
  sep_1 = ": ", sep_2 = ": ", env_prior = parent.frame())

composerr_parent(text_1 = NULL, err_prior = NULL, text_2 = NULL,
  sep_1 = ": ", sep_2 = ": ", env_prior = parent.frame())

Arguments

text_1

A character string, which will be appended at the beginning of the error message. The argument sep_1 will be used as text separator.

err_prior

There are three valid types:

• err_prior is omitted: A new error handling message will be returned.

• composerr_ is the calling function: err_prio must be a character string holding the name of the error handling function to which the message part should be appended.

• composerr is the calling function: err_prio must be the error handling function to which the message part should be appended.

text_2

A character string, which will be appended at the end of the error message. The argument sep_2 will be used as text separator.

sep_1

A character string that is used as separator for the concatenation of text_1 at the beginning of the error message.

sep_2

A character string that is used as separator for the concatenation of text_2 at the end of the error message.

env_prior

An environment where the error handling function given in err_prior can be found. If no environment is given, then the err_prior will be looked up in the current environment. In the situation of nested scopes, you may change the lookup environment to the parent environment in order to be able to recursively override the name of the error handling function. In order to keep it simple, the function composerr_parent() can be used instead.

Value

A new error handling function that has an extended error message.