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Forum: X3J13 Letter Ballot

References: (pp22-7..22-8), (p22-9)


Edit history: 16-Jun-93, Version 1 by Pitman

Status: Proposal JUST-ONE-SPACE passed (7+1)-3 on letter ballot 93-304

Problem Description:

In the descriptions of how lists and vectors print, the draft

standard says "whitespace" is printed where CLtL1 says "a space".

Is this an unintentional change?


When *print-pretty* is false, require the printer to use exactly

one space in the indicated situations. In general, when *print-pretty*

is false, recommend that implementations and users output a minimum

of space in this situation. [This is status quo under CLtL1]

Rationale: This forces implementations to use very little space

and makes printer behavior more regular across implementations.


Affirm that where the printer is defined to output whitespace,

arbitrary whitespace is permissible. Recommend that implementations

and users use a minum of whitespace when *print-pretty* is false,

but permit flexibility. [This is status quo under dpANS]

Rationale: This makes it less likely that users will write code

that is not robust in the face of varying amounts of

whitespace inserted by entities other than the printer

(e.g., a human being).

Test Cases:

#1: (CHAR (FORMAT NIL "~S" '(A B)) 2)

might return #\Space in some implementations and #\Newline in others.

#2: (CHAR (FORMAT NIL "~S" '(A B)) 3)

might return #\Space in some implementations and #\B in others.

#3: (LENGTH (FORMAT NIL "~S" '(A B)))

might return 5 in some implementations or greater numbers in others.

Current Practice:

Not provided.

Cost to Implementors:

JUST-ONE-SPACE: Relatively small.

WHITESPACE: None. (status quo)

Cost to Users:


WHITESPACE: None. (status quo)

Cost of Non-Adoption:

See Rationale above.


See above.

Editorial Impact:



Some people might quibble a little, but mostly pretty neutral.


This is in response to Public Review comment Loosemore #15.

Pitman prefers option WHITESPACE.

Pitman believes the complained-about change occurred during

the integration of the pretty printer description with the

printer chapter. At Waters' direction, he allowed this change

to be taken as editorial--probably a bad idea in retrospect.

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