2015年3月1日 · By way of explanation, everything is an expression, and there is nothing particularly special about functions. You and I know that this definition doesn't have lot of meaning for objects "u" that aren't functions, but Mathematica doesn't need to know that u is a function.

2011年10月3日 · Since the piecewise function you want is quite simple, it could also be constructed from step functions like Boole, UnitStep and UnitBox, e.g. UnitBox[(x + 4)/2] + UnitBox[(x - 2)/2] These are just special cases of Piecewise , as shown by PiecewiseExpand

2012年9月22日 · The way to "define" a function without specifying an expression is to not define it. Just use it. Example: D[f[x] g[x],x] (* ==> g[x] f'[x] + f[x] g'[x] *) As you can see, I didn't define f or g, and yet Mathematica has no problems calculating with them. Note that you can also make definitions using those functions. For example:

I will give an elaborate answer because I think this is an area where Mathematica really shines ;) Let me digress. We know that, in general, an equation system defines a set of points as a function of the parameters in it. Namely, the set of variable assignments or …

2018年3月15日 · I think it's easier just to define this straight up, rather than compute something procedurally. f[1, 0] = 77; f[0, 1] = 66; f[_, _] = 0; Mathematica is fundamentally an expression rewriting system, so telling it how to rewrite expressions directly like this is usually clearer, faster, and easier to debug.

2021年11月24日 · $\begingroup$ If you just write f[t] and f[t] was not defined anywhere, Mathematica will leave it as f[t] and not replace it by any definition. So you can just use f[t] like this for your function. Mathematica is by default symbolic, You do not need to use syms like with Matlab. $\endgroup$ –

2011年4月4日 · look at a, b and c as the first, second and third argument at the function call and NOT symbols a,b or c. Similar as in f := (#1 + #2 + #3)& , the call to f itself (without arguments) will not give desired results.

Accessing global variables from inside a function is not a good way to do things (tm). It is better to do it the good old fashioned way, and put the body of the function inside the function, and pass it all its input via arguments. f[t_, x_] := Cos[t] + x The difference is important.

2014年2月18日 · In the first approach mathematica doesn't evaluate anything, just leaving the even function with whatever its argument is, and in the second approach I have a lot of #'s that are left unevaluated as well. $\endgroup$

Use a doble underscore (triple if you want your function to accept no arguments at all): f[x__] := List[x] This is an example. f[1] {1} f[1,2] {1,2} You can specify the type of argument, and you can also have composite data structures like sequences of two element lists, for example.