The Fortress Language Specification - CiteSeerX

U+0021 EXCLAMATION MARK ! U+0023 NUMBER SIGN #
U+0024 DOLLAR SIGN $ U+0025 PERCENT SIGN %
U+002B PLUS SIGN + U+002D HYPHEN-MINUS −
U+003F QUESTION MARK ? U+0040 COMMERCIAL AT @
U+002A ASTERISK * U+002F SOLIDUS /
U+003C LESS-THAN SIGN < U+003E GREATER-THAN SIGN >
U+007E TILDE ˜
and most (but not all) Unicode characters specified to be mathematical operators (i.e., characters with code
points in the range 2200-22FF) are operators in Fortress.
• other characters
Some other classes of characters, which overlap with the ones above, are useful to distinguish:
• control characters are those with Unicode general category Cc;
• ASCII characters are those with code points U+007F and below;
• printable ASCII characters are ASCII characters that are not control characters (i.e., with code points from
U+0020 to U+007E);
• word characters are letters, digits, connecting punctuation, prime characters, and apostrophe;
• restricted-word characters are ASCII letters, ASCII digits, and the underscore character (i.e., ASCII word
characters other than apostrophe);
• hexadecimal digits are the digits and the letters A, B, C, D, E and F;
• operator characters are special operator characters and ordinary operator characters;
• special characters are special non-operator characters and special operator characters;
• enclosing characters are the enclosing operator characters enumerated in Section F.1, left and right parenthesis
characters, and mathematical left and right white square brackets;
• operator combining characters, which combine to form multicharacter enclosing operator tokens, are the following:
U+0028 LEFT PARENTHESIS ( U+0029 RIGHT PARENTHESIS )
U+002A ASTERISK * U+002E FULL STOP .
U+002F SOLIDUS / U+003C LESS-THAN SIGN <
U+003E GREATER-THAN SIGN > U+005B LEFT SQUARE BRACKET [
U+005C REVERSE SOLIDUS \ U+005D RIGHT SQUARE BRACKET ]
U+007B LEFT CURLY BRACKET { U+007C VERTICAL LINE |
U+007D RIGHT CURLY BRACKET }
Forbidden Characters
It is a static error for a Fortress program to contain any control character other than the above-listed whitespace
characters, except that the character SUBSTITUTE (U+001A; also known as “control-Z”) is allowed and ignored if it
is the last character of the program.
It is a static error for the following characters to occur outside a comment:
U+0009 CHARACTER TABULATION U+000C LINE TABULATION
U+001C INFORMATION SEPARATOR FOUR U+001D INFORMATION SEPARATOR THREE
U+001E INFORMATION SEPARATOR TWO U+001F INFORMATION SEPARATOR ONE
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