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| ANSI Common Lisp 2 Syntax 2.1 Character Syntax 2.1.4 Character Syntax Types ### 2.1.4.2 Constituent Traits Every character has one or more constituent traits that define how the character is to be interpreted by the Lisp reader when the character is a constituent character. These constituent traits are alphabetic2, digit, package marker, plus sign, minus sign, dot, decimal point, ratio marker, exponent marker, and invalid. Figure 2.1.4.2 Constituent Traits shows the constituent traits of the standard characters and of certain semi-standard characters; no mechanism is provided for changing the constituent trait of a character. Any character with the alphadigit constituent trait in that figure is a digit if the current input base is greater than that character's digit value, otherwise the character is alphabetic2. Any character quoted by a single escape is treated as an alphabetic2 constituent, regardless of its normal syntax.
constituent character | traits | constituent character | traits
--- | --- | --- | ---
Backspace | invalid | { | alphabetic2
Tab | invalid* | } | alphabetic2
Newline | invalid* | + | alphabetic2, plus sign
Linefeed | invalid* | - | alphabetic2, minus sign
Page | invalid* | . | alphabetic2, dot, decimal point
Return | invalid* | / | alphabetic2, ratio marker
Space | invalid* | A, a | alphadigit
! | alphabetic2 | B, b | alphadigit
" | alphabetic2* | C, c | alphadigit
# | alphabetic2* | D, d | alphadigit, double-float exponent marker
$ | alphabetic2 | E, e | alphadigit, float exponent marker
% | alphabetic2 | F, f | alphadigit, single-float exponent marker
& | alphabetic2 | G, g | alphadigit
' | alphabetic2* | H, h | alphadigit
( | alphabetic2* | I, i | alphadigit
) | alphabetic2* | J, j | alphadigit
* | alphabetic2 | K, k | alphadigit
, | alphabetic2* | L, l | alphadigit, long-float exponent marker
0-9 | alphadigit | M, m | alphadigit
: | package marker | N, n | alphadigit
; | alphabetic2* | O, o | alphadigit
< | alphabetic2 | P, p | alphadigit
= | alphabetic2 | Q, q | alphadigit
> | alphabetic2 | R, r | alphadigit
? | alphabetic2 | S, s | alphadigit, short-float exponent marker
`@` | alphabetic2 | T, t | alphadigit
] | alphabetic2 | U, u | alphadigit
\ | alphabetic2* | V, v | alphadigit
[ | alphabetic2 | W, w | alphadigit
^ | alphabetic2 | X, x | alphadigit
_ | alphabetic2 | Y, y | alphadigit
` | alphabetic2* | Z, z | alphadigit
| | alphabetic2* | Rubout | invalid
~ | alphabetic2 |  |
Constituent Traits of Standard Characters and Semi-Standard Characters
The interpretations in this table apply only to characters whose syntax type is constituent. Entries marked with an asterisk (*) are normally shadowed2 because the indicated characters are of syntax type whitespace2, macro character, single escape, or multiple escape; these constituent traits apply to them only if their syntax types are changed to constituent.

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