[erlang-questions] How to make this work

Roelof Wobben <>
Wed Aug 12 17:42:09 CEST 2015


Hello,

According to the Programming Erlang book second edition this is the 
proper syntax.

Double = fun X -> X * 2 end.

Roelof


Op 12-8-2015 om 17:38 schreef Garry Hodgson:
> read the documentation on the proper syntax for defining funs.
>
> On 8/12/15 11:34 AM, Roelof Wobben wrote:
>> 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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