Issue COPY-SYMBOL-PRINT-NAME Writeup

Issue:        COPY-SYMBOL-PRINT-NAME

References:   COPY-SYMBOL (p. 169)

Category:     CLARIFICATION

Edit history: 1-MAR-89, Version 1 by Chapman

              15-MAR-89, Version 2 by Chapman

 

Problem Description:

 

The description of COPY-SYMBOL states that it "returns a new uninterned

symbol with the same print name as sym (its first argument)". The words

"the same as" are not defined in CLtL. Do they mean EQ, EQUAL, ...?

 

Proposal (COPY-SYMBOL-PRINT-NAME:EQUAL)

 

The description of COPY-SYMBOL should read as follows:

"COPY-SYMBOL returns an uninterned

symbol whose print name is STRING= to

the print name of the symbol that is the first argument to COPY-SYMBOL."

 

Suggested implementation note:

The string should not be copied unnecessarily. In this case, the uninterned

symbol's print name would be EQ to the print name of the argument symbol.

 

Rationale:

 

This clarification resolves any possibility of ambiguity.

 

Current Practice:

 

Medley did this: the symbol names didn't really have a string header and

some symbol names (the "initial symbols" ) had a different place for

storing the actual characters than symbols created later. Unfortunately,

that means that SYMBOL-NAME has to CONS.

It wasn't so much a problem for Interlisp since most of the "string"

functions in Interlisp will take symbols, but in Common Lisp, it is a

performance hit. Poor design, but there's no reason to require SYMBOL-NAME

to return EQ strings. 

In this case, the strings aren't EQ even though the string characters are

shared. (Think of it as strings displaced to a shared area.)

 

 

Adoption Cost:

 

?

 

Benefits:

 

Less ambiguity in the specification, and potentially more portable code.

 

Conversion Cost:

 

?

 

Aesthetics:

 

None.

 

Discussion: