read ?package input
reads a full name from input.
This function will parse the input
and return a fully-qualified name that corresponds to the input, using package
as the currently opened package. The input syntax is
name = string, ":", string
| ":", string
| string
string = ?a sequence of any characters?
Not all characters in the input
string are treated literally, the following two characters have a special interpretation:
'\\'
the escape character;':'
the package separator character.
The escape character disables a special interpretation of the consequent character. The package separator denotes the place in the input where the package name ends and the name part starts.
If package
is specified then it is treated literally (as in the create
function). The same as in create
it defaults to the "user"
package.
If input
doesn't denote a fully qualified name (i.e., there is no ':'
special character in input
, then the read name is qualified with the passed package
, otherwise the package is defined by the input
.
The function is expected to work with the output of the show
function, so that for all n
, read (show n) = n
. However, it is robust enough to accept any user inputs, even if it is not a well-formed input, e.g., when an escape character is used to escaped a non-special character or when input contains more than one unescaped separators. In case of invalid input, all special characters that doesn't make sense are treated literally and the first special ':'
denotes the end of the package field. If the input is not valid, then it is possible that show (read s) <> s
, since the output of show
is always valid, e.g.
show@@read "hello:cruel:world" = "hello:cruel\\:world"