The Fortress Language Specification - CiteSeerX

Here are examples of function declarations whose bodies are do expressions:
f(x : R64) = do
(sin(x) + 1) 2
end
foo(x : R64) = do
y = x
z = 2x
y + z
end
mySum(i : Z64) : Z64 = do
acc : Z64 := 0
for j ← 0 : i do
acc := acc + j
end
acc
end
13.11.1 Generated Expressions
If a subexpression of a do expression has type (), the expression may be followed by a ‘ , ’ and a generator list
(described in Section 13.17). When a generator list is provided, generators produce values and bind the values to the
identifiers that are used in the preceding expression. Most generators, unlike the sequential generator, may execute
each evaluation of the assignment in a separate implicit thread.
13.11.2 Distinguishing a Local Declaration from an Equality Expression
Because a local declaration shares a syntax with an equality expression, we provide rules for disambiguation:
• If an expression of the form “e = e ” occurs as a proper subexpression in any non-block expression, it is an
equality expression.
• If such an expression occurs as an immediate subexpression of a block expression, it is a local declaration.
Adding parentheses makes the expression an equality expression.
13.12 Parallel Do Expressions
Syntax:
Do ::= do BlockElem + also Do
| at Expr Do
A series of blocks may be run in parallel using the also do construct. Any number of contiguous blocks may be
joined together by the special reserved word also . Each block is run in a separate implicit thread; these threads
together form a group. A thread can be placed in a particular region by using an at expression as described in
Section 32.7.
For example:
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