Implement a lists:map using case clauses instead of function clauses in Erlang

Question

Can anyone tell me what this means? I am new to this and my friend recommended me to post in this website. By the way I'm new to Erlang.

If possible I want to write a code in editor and I don't even understand the question any sample input/output and how it works an explanation will do. Thankyou

Answer 1

Here's a simple example showing how to use function clauses, then case statements to do the same thing. Put the following code in a file named a.erl in some directory:

-module(a).
-export([show_stuff/1, show_it/1]).

show_stuff(1) ->
    io:format("The argument was 1~n");
show_stuff(2) ->
    io:format("The argument was 2~n");
show_stuff(_)->
    io:format("The argument was something other than 1 or 2~n").

show_it(X) ->
    case X of
        1 -> io:format("The argument was 1~n");
        2 -> io:format("The argument was 2~n");
        _ -> io:format("The argument was something other than 1 or 2~n")
    end.

Note that the file name, a.erl and the module directive:

-module(a).

must match. So, if you named your file homework1.erl, then the module directive in the file must be:

-module(homework1).

To save a lot of typing, it's best to use very short module names (as you will see below).

In a terminal window, switch directories to the directory containing a.erl:

 ~$ cd erlang_programs/

then launch the erlang shell:

 ~/erlang_programs$ erl
Erlang/OTP 24 [erts-12.0.2] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1]

Eshell V12.0.2  (abort with ^G)

Next, execute the following statements:

1> c(a).   <--- Compiles the code in your file 
{ok,a}     <--- Or, you may get errors which must be corrected, then try recompiling.

2> a:show_stuff(1).
The argument was 1
ok

3> a:show_stuff(4).
The argument was something other than 1 or 2
ok

4> a:show_it(1).
The argument was 1
ok

5> a:show_it(4).
The argument was something other than 1 or 2
ok

6> 

Note the syntax for calling a function defined in a file/module:

 module_name:function_name(arg1, arg2, ... argn).