# Tag Info

17

You seem to be re-evaluating the eigenvalues at every point. Just use this definition: Clear[Eval,kx, ky, kz]; Eval[kx_, ky_, kz_] = FullSimplify[ Eigenvalues[H[kx, ky, kz] + Subscript[H, 1][kx, ky, kz]]]; Then the plots will be faster. This will symbolically evaluate the eigenvalues once, and the variables kx, ky, kz get substituted into the ...

9

The two examples in this question relate to two different aspects of pattern matching. I will start with the simpler to understand and intentional aspect, which is the second example. g[2] /. g[ 1 + (1|other) ] -> post (* g[2] *) In the above, the pattern doesn't match, and it can never match. g[2] has one argument. Since Plus is OneIdentity, 2 ...

8

I think an acceptable solution is to Thread over Alternatives: Basic solution: SetAttributes[f, Flat]; f[a, b, c] /. Thread[f[a, f[b, c] | other], Alternatives] -> post post Though, it won't be very helpful in more complex situations: f[a | b, f[b, c | h]]. General solution (experimental) tupplesOver[ f[a | g, f[b, c | h] | other], ...

4

I think this is what you are looking for: BooleanTable[Xor[p, p || q], {p}, {q}] // TableForm

4

Personally, I find this behavior somewhat surprising -- in particular, I would intuitively expect the following patterns to be completely equivalent: somePattern[..., a|b, ...] somePattern[..., a, ...] | somePattern[..., b, ...] While that may seem a natural expectation I do not believe the documentation ever states that they are. Nowhere can I ...

3

After discussing with Kuba, I conjecture the following: Patterns involving alternatives are not evaluated further when attempting to match each alternative That is, somePattern[..., a|b, ...] originally evaluates as if a|b is a black box. Then, during pattern matching, the pattern does not evaluate any further when a|b is replaced by a and b in turn. To ...

2

If you are expecting Clear[x] to clear definitions of x, don't expect anything more from Clear[s]. So you can go with: X = 5; s = "X"; Clear[#] &@s X X Or, as pointed by Albert Retey, with Clear[Evaluate@s]. Maybe you don't want to use strings, then: X = 5; s = ToExpression["X", StandardForm, Unevaluated]; Clear[#] &@s X works too. Some ...

1

If $a$ is already defined SeedRandom[123]; a = RandomInteger[{1, 9}, 6] (* {8, 5, 1, 3, 7, 8} *) and Length[a]>=m then m = 4; a[[;; m]] = ConstantArray[0, m]; a (* {0, 0, 0, 0, 7, 8} *) However, if $a$ not already defined then create with length $m$ of zeros. m = 4; a = ConstantArray[0, m] (* {0, 0, 0, 0} *) Hope this helps.

1

I'm not sure that memoization applies to OPs question. In a direct test, the order doesn't seem to make much of a difference in execution time.

1

Will this simple method work for you? m = 5; Table[a[i] = 0, {i, m}];

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