patterns with rational numbers

[mnklann]

Hi, I have two questions regarding pattern matching with rational numbers.

In my example, I try to match half-integers using conditions, but this doesn’t seem to work. Is there a more straightforward way to express this pattern, rather than multiplying by two and matching integers?

The second issue concerns powers. I obtain expressions such as (x)^(1/2). What exactly are these objects? I couldn’t find anything about this in the documentation (I may have overlooked it).

S x,n;
CF f;

L F = f(-1/2) + f(-1);
id f(x?{<0}) = 0;
* expected result: F = 0
P+s;
* F = f(-1/2)
.sort

L F = x^(1/2);
id x^n? = x^(n+1);
* expected result: F = x^(3/2)
P+s;
* F = x^(1/2)*x
.end

[jodavies]

For the first case: maybe it only works for "fast notation"? f(-10000000000) (stored as 15 150 11 0 8 0 6 1410065408 2 1 0 -5 1 1 3) also does not match. The manual for neg_ etc all state "integers that fit inside a FORM word".

In the second case, (x)^(1/2) is the internal exp_ function. You can match with it as in Identify exp_(x,n?) = x^(n+1);

[tueda]

Though this is more of a tricky replacement rule than a pattern for matching half-integers, the following one-liner id statement discards f(-1/2), f(-3/2), etc.:

id f(x?number_) = f(x) * deltap_(1-delta_(x*2,x*den_)*thetap_(-x));