(j3.2006) (j3.2005) question on token replacement/concatenation

Aleksandar Donev donev1
Thu Nov 30 16:40:30 EST 2006


On Thursday 30 November 2006 11:23, Michael Ingrassia wrote:

>  3 %% .14159 %% E %% + %% 0
First, did you mean to put spaces after the 3, around the E, etc.? Is this 
fixed or free source form?

I ask because the token's in the concatenation must be *single* lexical 
tokens, which are defined as:
"Lexical tokens are sequences of characters that constitute the building 
blocks of a program. They are keywords, names, literal constants other than 
complex literal constants, operators, labels, delimiters, comma, =, 
=>, :, ::, ;, and %."

I don't think a token can have a space in it, at least not in free form:
"Blank characters shall not appear within lexical tokens other than in a 
character context or in a format specification."

>  "3.14159E+0" is not immune to
> change in its individual tokens via token replacement.  Right?
"3.14159%%E%%+0" is not immune, while "3.14159E+0"  is immune (that is, the E 
is an E no matter whether there is a macro argument/variable E).
The whole of "3.14159E+0" is a single token.

Eliminating the extra spaces around the %%,

3%%.14159%%8 D%%+0

 produces

3.141598     D+0

which in free source form violates the rule:

"C314 (R334) The concatenated textual tokens in a result-token shall have the 
form of a lexical token."

so it is not OK.

Aleks



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