Technical data

Working with the Target Language

2-22

%roll

The syntax of the %roll multiple inclusion directive is:

%roll ident1 = roll-vector-exp, ident2 = threshold-exp, ...

block-exp [, type-string [,exp-list] ]

%break

%continue

%endroll

This statement uses the roll-vector-exp to expand the body of the %roll

statement multiple times as in the

%foreach statement. If a range is provided

in the

roll-vector-exp and that range is larger than the threshold-exp

expression, the loop will roll. When a loop rolls, the body of the loop is expanded

once and the identifier (

ident2) provided for the threshold expression is set to

the name of the loop control variable. If no range is larger than the specified

rolling threshold, this statement is identical in all respects to the

%foreach

statement.

For example:

%roll Idx = [ 1 2 3:5, 6, 7:10 ], lcv = 10, ablock

%endroll

In this case, the body of the %roll statement expands 10 times as in the

%foreach statement since there are no regions greater than or equal to 10. Idx

counts from 1 to 10, and

lcv is set to the null string, "".

When the Target Language Compiler determines that a given block will roll, it

performs a

GENERATE_TYPE function call to output the various pieces of the loop

(other than the body). The default type used is

Roller; you can override this

type with a string that you specify. Any extra arguments passed on the

%roll

statement are provided as arguments to these special-purpose functions. The

called function is one of these four functions:

RollHeader(block, …). This function is called once on the first section of this roll

vector that will actually roll. It should return a string that is assigned to the

lcv within the body of the %roll statement.

LoopHeader(block, StartIdx, Niterations, Nrolled, …). This function is called once for

each section that will roll prior to the body of the

%roll statement.