I believe the first version of make required tabs, but some subsequent versions have relaxed that requirement to make things easier.

Here's an example on a Linux Mint system (the 20's are of course spaces) :
$ od -cx < Makefile
cmd output started 2015 Sat Nov 21 04:39:47 PM PST
0000000  \n   g   o   :  \n                   .   /   t  \n  \n
           670a    3a6f    200a    2020    2e20    742f    0a0a
0000016
above cmd output done    2015 Sat Nov 21 04:39:47 PM PST
dstromberg@dell-inspiron:/var/tmp/make-tabs i686-pc-linux-gnu 25234

$ make
cmd output started 2015 Sat Nov 21 04:39:48 PM PST
Makefile:3: *** missing separator.  Stop.
above cmd output done    2015 Sat Nov 21 04:39:48 PM PST
dstromberg@dell-inspiron:/var/tmp/make-tabs i686-pc-linux-gnu 25234

$ make --version
cmd output started 2015 Sat Nov 21 04:39:53 PM PST
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for i686-pc-linux-gnu
above cmd output done    2015 Sat Nov 21 04:39:53 PM PST
dstromberg@dell-inspiron:/var/tmp/make-tabs i686-pc-linux-gnu 25234

I'll add that vim's Makefile syntax highlighting puts the space-indented line in red, suggesting an error.  Changing the spaces to a single tab makes the red go away.

HTH

On Sat, Nov 21, 2015 at 3:34 PM, Thomas Jakway <tjakway@nyu.edu> wrote:

Why would make require tabs...?
Admittedly it's been a long time since I've written any makefiles by hand but I always use spaces instead of tabs and have never had any problems.

On Nov 21, 2015 6:01 PM, David Moberg <kaddkaka@gmail.com> wrote:
>
> Have you found "soft tabs"? That option will make TextMate use spaces instead of tab characters. Read 4.11 "Using Spaces Instead of Tabs" in Dan Strombergs link for instrucitons.
>
> 2015-11-21 21:36 GMT+01:00 Jeon-Young Kang <jykang22@gmail.com>:
>>
>> I've tried to choose "instead of spaces". But there is no option of mine (Textmate 2 beta).
>>
>> On Sat, Nov 21, 2015 at 3:14 PM, Dan Stromberg <strombrg@gmail.com> wrote:
>>>
>>>
>>> Perhaps enable soft tabs?
>>> https://manual.macromates.com/en/working_with_text
>>>
>>> This is an issue in Python too (at least from PEP8's perspective) - but note that many "make" programs require tabs instead of spaces.
>>>
>>> On Sat, Nov 21, 2015 at 11:13 AM, Jeon-Young Kang <jykang22@gmail.com> wrote:
>>>>
>>>> Hello everyone.
>>>>
>>>>
>>>> I am a newbie of Haskell, using Textmate on mac.
>>>>
>>>>
>>>> I got the following warning. How can I fix it?
>>>>
>>>>
>>>> Warning:
>>>>
>>>>     Tab character
>>>>
>>>> Ok, modules loaded: Main.
>>>>
>>>>
>>>>
>>>> Sincerely,
>>>> Young
>>>>
>>>> _______________________________________________
>>>> Beginners mailing list
>>>> Beginners@haskell.org
>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>>>
>>>
>>>
>>>
>>> --
>>> Dan Stromberg
>>>
>>> _______________________________________________
>>> Beginners mailing list
>>> Beginners@haskell.org
>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>>
>>
>>
>>
>> --
>> Department of Geography
>> State University of New York at Buffalo
>>
>> jykang22@gmail.com
>>  
>> Jeon-Young Kang
>>
>> _______________________________________________
>> Beginners mailing list
>> Beginners@haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>
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Dan Stromberg

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