[erlang-questions] How to make this work

[Roelof Wobben]

Hello,

Im trying this exercise from the programming erlang book.

Look up the definitions of erlang:now/0, erlang:date/0, and 
erlang:time/0. Write a
function called my_time_func(F), which evaluates the fun F and times how
long it takes.

So I did this :

-module(my_time).

-export( [time_spend/1] ).

time_spend(F) ->
     Begintime = time:now(),
     F(3),
     Endtime = time:now(),
     Endtime - Begintime.


but then when I do this in erl :

11> my_time:time_spend(fun x -> 2 * X end).
  * 1: syntax error before: '->'
11> my_time:time_spend(Double = fun x -> 2 * X end).
* 1: syntax error before: '->'

how can I make this work ?

Roelof


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