The Fortress Language Specification - CiteSeerX

Appendix G
Concrete Syntax
In this chapter, we describe the concrete syntax of Fortress programs in BNF notation. This syntax is “human-readable”
in the sense that it does not describe uses of whitespaces and semicolons exactly. Instead, they are described as follows.
Fortress has three different contexts influencing the whitespace-sensitivity of expressions:
statement Expressions immediately enclosed by a block expression are in a statement-like context. Multiple expressions
can appear on a line if they are separated (or terminated) by semicolons. If an expression can legally end
at the end of a line, it does; if it cannot, it does not. A prefix or infix operator that lacks its last operand prevents
an expression from ending. For example,
an = expression+
spanning+
four+
lines
a = oneLiner
four();on();one();line();
nested An expression or list of expressions immediately enclosed by parentheses or braces is nested. Multiple expressions
are separated by commas, and the end of a line does not end an expression. Because of this effect,
the meaning of a several lines of code can change if they are wrapped in parentheses. Parentheses can also be
used to ensure that a multiline expression is not terminated prematurely without paying special attention to line
endings.
lhs = rhs
−aSeparateExpression
postProfit(revenue
−expenses)
pasted Fortress has special syntax for matrix pasting. Within square brackets, whitespace-separated expressions are
treated (depending on their type) as either matrix elements or submatrices within a row. Because whitespace
is the separator, it also ends expressions where possible. In addition, newline-or-semicolon-separated rows are
pasted vertically along their columns. Higher-dimensional pasting is expressed with repeated semicolons, but
repeated newlines do not have the same effect.
id2a = [1 0; 0 1 ]
id2b = [1 0;
0 1 ]
id2c = [1 0
0 1 ]
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