[viff-devel] Vedr.: Small VIFF language parser

[Janus Dam Nielsen]

Hi again,

Heres the fruit of half a days work :)

Analyzing the expression:
    sint n = (a * y + (1 - a) * x);

Yields the following results:

Final result:
((a * y )+ ((1 - a )* x )) cost: 30
(((a * y )+ x )- (x * a )) cost: 30
(((a * y )+ x )- (a * x )) cost: 30
(((a * y )- (a * x ))+ x ) cost: 30
(((y * a )+ x )- (a * x )) cost: 30
(((y * a )+ x )- (x * a )) cost: 30
((a * y )+ (x - (x * a ))) cost: 30
(((y * a )- (a * x ))+ x ) cost: 30
(((y * a )- (x * a ))+ x ) cost: 30
(((a * y )- (x * a ))+ x ) cost: 30
((a * (y - x ))+ x ) cost: 20

And lo and behold the last line reveals that the expression
a * (y - x )+ x
has the lowest cost. Again I just used the 10,5,5 costs for multiplication,
addition, and subtraction (they seem to enough for the moment).

These 11 expressions are not all the possible expressions one could generate, so
I don't claim that my implementation is complete but I hope it is sound.

Later...