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Bug 7370 : FAQ errors about purity, implementation ease, and open source #70

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Merged
merged 3 commits into from
Feb 5, 2012
Merged

Bug 7370 : FAQ errors about purity, implementation ease, and open source #70

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5f32044
7370a FAQ talks about implementation ease
Jan 31, 2012
07c1923
7370b FAQ errors: purity and open source
Jan 31, 2012
b7d082d
FAQ: explain why we use the boost license
Feb 1, 2012
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66 changes: 27 additions & 39 deletions faq.dd
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Original file line number Diff line number Diff line change
Expand Up @@ -63,9 +63,9 @@ $(D_S $(TITLE),
$(ITEMR backend, How do I write my own D compiler for CPU X?)
$(ITEMR gui, Where can I get a GUI library for D?)
$(ITEMR ide, Where can I get an IDE for D?)
$(ITEMR q3, Why emphasize implementation ease?)
$(ITEMR q4, Why is [expletive deleted] printf left in?)
$(ITEMR q5, Will D be open source?)
$(ITEMR q5, Is D open source?)
$(ITEMR q5_2, Why does the standard library use the boost license? Why not public domain?)
$(ITEMR q6, Why $(I no) fall through on switch statements?)
$(ITEMR q7, Why should I use D instead of Java?)
$(ITEMR q7_2, Doesn't C++ support strings, etc. with STL?)
Expand Down Expand Up @@ -209,32 +209,6 @@ $(ITEM ide, Where can I get an IDE for D?)
$(LINK2 http://prowiki.org/wiki4d/wiki.cgi?EditorSupport, the D wiki).
)

$(ITEM q3, Why emphasize implementation ease?)

$(P Isn't ease of use for the user of the language more important? Yes,
it is.
But a vaporware language is useless to everyone. The easier a language
is to implement, the more robust implementations there will be. In C's
heyday, there were 30 different commercial C compilers for the IBM PC.
Not many made the transition to C++. In looking at
the C++ compilers on the market today, how many years of development
went into each? At least 10 years? Programmers waited years
for the various pieces of C++ to get implemented after they were
specified.
If C++ was not so enormously popular, it's doubtful that very complex
features
like multiple inheritance, templates, etc., would ever have been
implemented.
)

$(P I suggest that if a language is easier to implement, then it is
likely also easier to understand. Isn't it better to spend time learning
to write better programs than language arcana? If a language can capture
90% of the power of
C++ with 10% of its complexity, I argue that is a worthwhile tradeoff.
)


$(ITEM q4, Why is printf in D?)

$(P $(LINK2 http://www.digitalmars.com/rtl/stdio.html#printf, printf)
Expand All @@ -247,18 +221,33 @@ $(ITEM q4, Why is printf in D?)
)


$(ITEM q5, Will D be open source?)
$(ITEM q5, Is D open source?)

$(P The front end for the $(B dmd) D compiler is open source.
The back end for dmd is licensed from Symantec,
and is not compatible with open-source licenses such as the GPL.
Nonetheless, the complete source comes with the
$(LINK2 http://www.digitalmars.com/d/download.html, compiler),
and all development takes place publically on
$(LINK2 https://github.com/D-Programming-Language/dmd, github).
Compilers using the DMD front end and the GCC and LLVM open source
backends are also available.

$(P The front end for the $(B dmd) D compiler is open source, and the complete
source comes with the
$(LINK2 http://www.digitalmars.com/d/download.html, compiler),
and is available on $(LINK2 https://github.com/D-Programming-Language/dmd, github).
The back end for dmd is licensed from Symantec.
The runtime library is completely open source using the
$(LINK2 http://boost.org/LICENSE_1_0.txt, Boost License 1.0).
The $(B gdc) and $(B ldc) D compilers are completely open sourced.
)

$(ITEM q5_2, Why does the standard library use the boost license? Why not public domain?)

$(P Although most jurisdictions use the concept of Public Domain, some
(eg, Japan) do not.
The $(LINK2 http://boost.org/LICENSE_1_0.txt, Boost License)
avoids this problem. It was chosen because, unlike almost all other open
source licenses, it does not demand that the license text be included on
distributions in binary form.
)

$(ITEM q6, Why $(I no) fall through on switch statements?)

$(P Many people have asked for a requirement that there be a break between
Expand Down Expand Up @@ -693,7 +682,7 @@ $(V2

$(LI C++ code, despite decades of attempts to replace macro features
with inbuilt ones, relies more heavily than ever on layer after layer of
arbitrary macros. There is no D analog for token pasting or
arbitrary macros. D does not always have an analog for token pasting and
stringizing.)

$(LI Macro names have global scope across #include files, but are local
Expand Down Expand Up @@ -826,10 +815,9 @@ $(ITEM gc_1, Isn't garbage collection slow and non-deterministic?)

$(ITEM pure, Can't a sufficiently smart compiler figure out that a function is pure automatically?)

$(P The problems with the
$(LINK2 http://c2.com/cgi/wiki?SufficientlySmartCompiler, sufficently smart compiler)
argument are:
)
$(P The compiler infers purity (and safety, and nothrow) for delegate and function
literals. It doesn't do this for normal functions for several reasons:
)

$(OL
$(LI most functions call other functions, which call other functions,
Expand Down