Matching patterns in pure functions

Question

I need to define a pure function that takes two arguments and returns their quotient. If the divisor 0

, then I want to return 0

.

If I had a named function I would do

div[_, 0]   := 0
div[x_, y_] := x / y

how to do a similar pattern matching by arguments in a pure function #1 / #2 &

?

+3

akonsu June 12. 15 at 17:16

3 answers

Try something like

If[#2 == 0, 0, #1/#2] &

for your pure function.

+4

High Performance Mark June 12. 15 at 17:39

You can use a combination of Replace

and Condition

to achieve similar pattern matching to pure function arguments

Replace[_, {_ /; #2 == 0 -> 0, _ :> #1/#2}] &

for example

Replace[_, {_ /; #2 == 0 -> 0, _ :> #1/#2}] &[a, 2]

a/2

and

Replace[_, {_ /; #2 == 0 -> 0, _ :> #1/#2}] &[a, 0]

0

+1

Karsten 7. May 1 '16 at 18:41

agentp · Accepted Answer · 2015-06-15T13:27:46+0000

Switch

might be useful, for example:

Switch[ # ,
       _String , StringLength[#] ,
       _List , Length[#] , 
       __ , Null ] & /@ { "abc", {1, 2, 3, 4}, Pi}

{3, 4, Null}