Advanced Fortran Programming : 026 : Optional Parameters 2 and Array Valued Functions Video Lecture | Introduction to Fortran Programming (AdvancedLevel) - Database Management

hello guys my name is Aaron and welcome
to my channel okay this series is a
series of tutorials on advanced Fortran
programming and now in this tutorial
we'll be looking at an interesting
concept and which is this will be the
last concept using the interface option
available for tonight okay today we'll
be looking at our evaluate functions and
one more interesting one more topic
called as optional parameters now why
does an array valid function mean is
this as follows see as for now we have
seen functions okay which are made by us
which returns only a single value but
Vadis we have the facility to make that
a function return our entire array
instead okay now that will be in - that
will be very much beneficial in certain
aspects okay and if you want to make
that kind of a thing possible in Fortran
before then we have facilities and
Fortran allows that and we looking at
that today and also if looking at some
optional parameters you need certain
parameters which where if you need not
include on their own included necessary
but if they're included they'll have
they'll modify the conditions slightly I
mean they modify the conditions are
Cottingley
okay and if they are not included
they'll lose some they will not modify
me they may not do the same
modifications as and when they are
included and something of that sort
okay I'll walk you guys through the
program then you understand okay today
what we are going to do to explain this
to turn what we are going to do is that
to explain this optional parameters and
to explain array valued functions I have
written a small function over here
call us math math as the name suggests
it's going to be a smart fix
multiplication okay what it does is that
it takes two arrays a and B okay and an
optional parameter D and it draws the
matrix multiplication and the result is
in C okay
for that what I've done is that I need
three into three indices IJ and K okay
well indices I want C 1 R 2 C 2 R for
the rows and columns of the matrix one
and two okay s 1 s 2 are separate I'll
explain you guys how that works it's two
dimensional array I'll explain you that
B is the optional parameter and if you
want to declare any optional parameters
to the function which can be included
and need its need or may not be included
what I do is yes you have to use the
option key word now when this key word
optional is used the photo and compiler
looks to see whether this the variable
is present if it is present we by
default
if it's optional okay by default all the
variables in this list should be present
in it and if it's if the certain
variables give an optional it available
now against this caption key but need
not be present so what happens is that
here the compiler will check for a B and
D and sometimes if D is not passed it
will check whether it's an optional
argument okay if it's an optional
optional argument it just ignore if it's
not then you throw an error me it'll
just check okay and then I'm just
getting the values a and B here and and
this little syntax is just for you know
allocating the size of matrix Isis I
know the value C L you see over here
this is the simple point is the size
function it has a total size of the
array okay and so what I did is that I
just allocating the matrix C to have the
number of rows of matrix a and the
number of columns of matrix B that's
that's the reason for the entire
complicated like a big expression but
nothing much and then using this I'd get
the shapes of a and matrix a and B using
the very functions shape and then using
the values s1 and s2 from which I assign
R 1 C 1 R 2 C 2 the row and column of
matrix 1 and the row and column of
matrix 2 using the valleys s1 and s2
and then initialize C to be zero okay
now what I do is that how to do is that
I just explain this part little later
okay now by matrix multiplication the
first thing you have to cry the first
grader you have to do is this okay
the number of columns and the first
matrix should be equal to the number of
rows in the second Matrix okay
now only when this condition is
satisfied this condition is satisfied
since C is already declared to be 0 on
the top okay
this looping of this looping setup will
do the matrix multiplication well do the
matrix multiplication and then returns
the circlet on modify the value C and
then and then since this matrix
multiplication times C the function will
return C and that's it oh okay
now I'll explain now this part is okay
just conventional and I let me explain
the optional parameter part of it
see see if B is present what I'm going
to do here is that if if I pass the
value D and this D is an integer this
can be any value as of now in this for
this program okay what I've done is that
if I pass D over here okay now this
comma press this function present is
used for determining whether the
optional parameter is plugged into the
function or not what it does is that it
checks this function this function takes
whether the partial parameter is present
in the function or not if it is present
this will return this will return a true
value and if this is true then this
function will execute all the statements
over here so that's essentially what it
means is that when this function after
the two matters is a and B if I just
return any integer okay this this entire
statement will be true okay and so what
it does is it just it just prints all
this print statements now essentially
this is just a debugging part and if you
don't and if you if you just ignore the
value D okay this part but this will
this will be will not be present inside
the function when is this pass so this
will be false
the entire set of intersections within a
function it is if contact will not be
executed simple as that
okay and with this I'll explain you guys
the options parameter and then let I'll
explain you guys how the I value
function looks like now this function so
far so far so good
okay sorry about that I think my phone
was in Milan anyway coming back as far
as we seen this function does all the
job nicely and the size of C is
determined over here but we have a small
problem over here what happens is that
see this function is written outside the
program so if it's out written outside
the program then sometimes if you just
know I'll show you guys let's have it
I just has a interface for interface
function written away interface function
part right over here okay if I just if I
just comment this some of these parts I
mean these parts take excessive and if I
had to add this add more function over
here
okay so how to do this if I were to
compile this okay they were to compile
this I'll I'm getting an error stating
like I'm getting here like this explicit
interface required format underscore
month at one I assumed shape argument so
problem here the problem here is
sometimes when you define a function
like this outside when you define a
function like this which has a non not
the modal say whose shape is more than
one okay and which is outside the
program like this this may not work and
suppose okay so you might be thinking
like okay the external parameter maybe
the issue
remove this okay and if I were to
compare this again I still get the same
warning so the point here is external
keyword is not the problem but the
problem the problem here is an
interfacing okay external functions
which are defined external to the
program with with with with it not
within the bounds of not within the
bounds of a module okay
they will have if you they will have
this table has this kind of a problem
and they are compiled like this so how
do we do that simple see what you do is
this for these functions you have to
interface this function and how do you
do that it's simple okay now let me just
comment this part over here and this
interface it path this is the program
okay program is after the score i func
meaning optional parameters and that
means that's what I am going to do here
I've just said here I'm just setting the
values of the rows and columns to
mattresses they are actually first
mattress is three rows and two columns a
second man that says two rows and three
columns and all of them are said to work
and see I'm not setting it to any
commenting this out okay let me um let
me uncover this comment this now this
interfacing why I've done I said I give
it the interface name is Matt and within
this interface within this interface
what I've included is that I've included
the function Matt underscore month which
is nothing but this function matt
underscore month okay and along with
that I've included all the intent in and
all the variables that are used within
the function okay
only that variability clear essence
sometimes you know this might work
without with only the internal
parameters and
other parameters I guess but to be on
the safe side
sorry do we have to say if I said I've
included all of them so now with this
what happens is if I were to compare
this after including the interface
functions he just works fine okay and he
forgot to build this it works fine again
and if I were to execute this it works
fine it works fine now
now because of this interfacing function
because of this interfacing feature I
have two options now I can use this
function Matt well acid test at the same
time even if I were to use that along
with it compact will not run this they
just run fine okay now if I were to
change this to just to your
application if I were to change this to
Matt well if I were to compile mill then
and this okay both of them work fine so
because of this interfacing function
interfacing facility okay
any function which now this function can
return an array value can determine
array and that's the advantage you have
because of this interface function and
this is nothing but gesture this is
nothing but you know formatting
formatting state lines to print the
matrix nicely this is me if you guys
remember we were we were discussing this
in one of the law previous tutorials
okay
nothing that nothing much special about
it and about regarding the optional
parameter I'll explain you guys if I
were to compile and run this again okay
to compile and run this again see okay
as of now and we part when we call this
function matter miss former okay along
with a and B are just giving an option
value three okay so Mary 3 okay
it may not be three okay since this
third this third argument
Dementors present okay that this
function gets called this present this
funk this line present of D is true
because they're optional argument is
present and because of when the since
that is present this entire set of
statement this debugging on statement
and everything with elusive constructors
getting printed over here and that is
what you see over here okay now what I
do is that is that I just remove this
three I just remove this three okay
not I just keep this here I went out
okay
I'll comment this out and this way you
guys can have a look I'm compatible
there and this okay if you guys noticed
since I've removed this option argument
right now okay everything within this
print statement has not been printed has
not been easy I mean within the skit
cousin is not executed whereas only the
resulting product matrix is only printed
displayed okay now that's how you use an
ad that's how you use an optional
argument now if this this is just one
simple the demonstration but if optional
argument has multiple values and stuff
and even if it's given not given you can
you can use lot of you know you can use
other automatic and constructs and
diction making statements accordingly to
make other options available and not
only that not only that based on the
presence of the statements messes of the
optional parameters you can do you can
do a little more job recording me okay
let's just meet you just have to let
your imagination the imagination it
while depending on the nature of the
program and just to make just to give an
alternate explanation alternate a
possibility okay
but it suppose if you want to make an
array valued function like this okay but
you don't want to use the interface
option what I'll do is simple right the
cinema right this inner module right the
same function you know inside of module
like what I've done over here okay this
is exactly the same function same
function okay I just included this
inside a module called as matrix okay
and and I ended I ended the module over
here and then in this function I mean
the program I include the module matrix
okay I've commented everything out and
then if I run this simple as that it
just runs fine okay and if I were to you
know if you guys are not I miss enough
comparable run this yeah it works fine
okay
similarly let's try me this isn't a
separate function so you can do a
separate program so you can try
economies now let's do a little trickery
since D is integer the passing only
integer so regardless of whatever it is
you go past this would work now if I
were to play or play something but let's
do something we'll do tricky let's do
something like let's pass and make it a
decimal number like sixty five point
eight this is decimal to compile okay
now you have an issue something like it
so it shows that type mismatch an
argument D passed real for the de jure
for now that's an issue what it says is
that now you are not allowed
you are not at all allowed to changes
change the data type though these are
optional arguments either you're not
allowed to change the argument that were
to change the data type as if I just
hide 66-65 or something how to compile
this it just works fine
and run this they just work for him so
the point here is even if you have
option arguments that does not mean
you're allowed to change the data type
accordingly the relative has to movement
whether they present or not it's
optional that's why if they're called as
optional arguments that's all I have for
you guys in this tutorial thank you guys
for watching
and in the next tutorial on words you'll
be looking at some even more complicated
not complicated even more advanced
features and this is regarding a file
processing in the previous tutorial we
saw I mean the previous tutorial series
we saw some examples where and we wrote
some contents into files okay and this
to tour the next cloud coming tutorials
at least I don't know three or four
tutorials I'm not sure how many okay you
know so turrets may be looking at some
advanced fie advanced file processing
commands available in Fortran and if
everything goes well maybe after that
they will be looking at looking at
pointers pointers and little more top
and some more topics here and there
which where I thought of there I have
which I've left and now and then mostly
mostly a little more color upon cover up
on those topics and then I'll toot other
things will come to an end thank you
guys for watching and see you guys next
adder so take care