Advanced Search
All Posts : Product Suggestions

Patterns in Replacement Rules

Mad Math 8
December 14 2005
0
There is one thing which, as far as I know (please correct me if I'm wrong), you can do with other languages like FORM and MATHEMATICA, but cannot do with MAPLE. That is, to use patterns in replacement rules. If this were included in a future version of MAPLE, I wouldn't use MATHEMATICA ever again! For example, in MATHEMATICA you can write the following input: f[{a,b}] + f[c] /. f[{x_,y_}] -> p[x+y] and then you get the following output: f[c]+p[a+b] Another example, {1,x,x^2,x^3} /. x^n_ -> r[n] then you get {1,x,r[2],r[3]} The underscores are used to mean "any expression". For example, x_ means any expression to be named x. MATHEMATICA also has things like x__ (x with two underscores), which means any sequence to be named x, and x___ (three underscores) which means any sequence of zero or more expressions to be named x. In FORM you have something similar, but instead of an underscore you use an interrogation sign, so x? would play the role in FORM that x_ plays in MATHEMATICA. In case you are not familiar with it, you can go to http://www.nikhef.nl/~form/ and have a closer look at this outstanding program, which by the way is free! (and also by the way, FORM has a few other things that might as well be worth including in MAPLE too, like the Levi-Civita tensor, and the trace of a product of Dirac gamma matrices). This kind of stuff is very powerful, as it allows you to write in one line what otherwise might take several lines of programming. If I'm mistaken, and this is actually already possible with the current version of MAPLE, I would like to know about it. Otherwise, it would be great if this improvement were made.

Please Wait...