diff --git a/fortran.html.markdown b/fortran.html.markdown
index 83074073..299f99ba 100644
--- a/fortran.html.markdown
+++ b/fortran.html.markdown
@@ -30,7 +30,8 @@ program example ! declare a program called example.
! All declarations must come before statements and expressions.
- implicit none ! prevents dynamic declaration of variables (recommended!)
+ implicit none ! prevents dynamic declaration of variables
+ ! Recommended!
! Implicit none must be redeclared in every function/program/module...
! IMPORTANT - Fortran is case insensitive.
@@ -45,10 +46,14 @@ program example ! declare a program called example.
complex :: w = (0, 1) ! sqrt(-1)
character(len=3) :: month ! string of 3 characters.
- real :: array(6) ! declare an array of 6 reals.
- real, dimension(4) :: arrayb ! another way to declare an array.
- integer :: arrayc(-10:10) ! an array with a custom index.
- real :: array2d(3, 2) ! multidimensional array.
+ ! declare an array of 6 reals.
+ real :: array(6)
+ ! another way to declare an array.
+ real, dimension(4) :: arrayb
+ ! an array with a custom index -10 to 10 (inclusive)
+ integer :: arrayc(-10:10)
+ ! A multidimensional array.
+ real :: array2d(3, 2)
! The '::' separators are not always necessary but are recommended.
@@ -76,8 +81,8 @@ program example ! declare a program called example.
! Assignment & Arithmetic
! =======================
-
- Z = 1 ! assign to variable z declared above (case insensitive).
+
+ Z = 1 ! assign to variable z declared above
j = 10 + 2 - 3
a = 11.54/(2.3*3.1)
b = 2**3 ! exponentiation
@@ -86,7 +91,7 @@ program example ! declare a program called example.
! ===================================
! Single-line if statement
- if (z == a) b = 4 ! condition always need surrounding parentheses.
+ if (z == a) b = 4 ! conditions always need parentheses.
if (z /= a) then ! z not equal to a
! Other symbolic comparisons are < > <= >= == /=
@@ -98,13 +103,13 @@ program example ! declare a program called example.
b = 5 ! execution block must be on a new line.
else
b = 10
- end if ! end statement needs the 'if' (or can use 'endif').
+ end if ! end statement needs the 'if'
if (.NOT. (x < c .AND. v >= a .OR. z == z)) then ! boolean operators.
inner: if (.TRUE.) then ! can name if-construct.
b = 1
end if inner ! then must name endif statement.
- end if
+ endif ! 'endif' is equivalent to 'end if'
i = 20
select case (i)
@@ -128,16 +133,16 @@ program example ! declare a program called example.
j = -1
end select monthly
- do i = 2, 10, 2 ! loops from 2 to 10 (inclusive) in increments of 2.
+ do i = 2, 10, 2 ! loops from 2 to 10 (inclusive) in steps of 2.
innerloop: do j = 1, 3 ! loops can be named too.
exit ! quits the loop.
end do innerloop
cycle ! jump to next loop iteration.
end do
- ! Goto statement exists but it is heavily discouraged though.
+ ! Goto statement exists but it is heavily discouraged.
goto 10
- stop 1 ! stops code immediately (returning specified condition code).
+ stop 1 ! stops the program, returns condition code 1.
10 j = 201 ! this line is labeled as line 10
! Arrays
@@ -209,8 +214,12 @@ program example ! declare a program called example.
! we can have multiple format specifications.
print "(I5,F6.2,E6.2)", 120, 43.41, 43.41
- print "(3I5)", 10, 20, 30 ! 3 repeats of integers (field width = 5).
- print "(2(I5,F6.2))", 120, 43.42, 340, 65.3 ! repeated grouping of formats.
+
+ ! 3 repeats of integers (field width = 5).
+ print "(3I5)", 10, 20, 30
+
+ ! repeated grouping of formats.
+ print "(2(I5,F6.2))", 120, 43.42, 340, 65.3
! We can also read input from the terminal.
read (*, *) v
@@ -225,8 +234,9 @@ program example ! declare a program called example.
! To read a file.
open (newunit=m, file="records.txt", status="old")
- ! The file is referred to by a 'new unit number', an integer that the compiler
- ! picks for you.
+ ! The file is referred to by a 'new unit number',
+ ! an integer that the compiler picks for you.
+
read (unit=m, fmt="(3F10.2)") a, b, c
close (m)
@@ -241,7 +251,7 @@ program example ! declare a program called example.
call cpu_time(v) ! sets 'v' to a time in seconds.
k = ior(i, j) ! bitwise OR of 2 integers.
v = log10(x) ! log base 10.
- i = floor(b) ! returns the closest integer less than or equal to x.
+ i = floor(b) ! converts b to integer by rounding down.
v = aimag(w) ! imaginary part of a complex number.
! Functions & Subroutines
@@ -252,7 +262,7 @@ program example ! declare a program called example.
call routine(a, c, v) ! subroutine call.
- ! A function takes a list of input parameters and returns a single value.
+ ! A function takes several input parameters and returns a single value.
! However the input parameters may still be modified and side effects
! executed.
@@ -261,21 +271,22 @@ program example ! declare a program called example.
! Function calls can also be evoked within expressions.
print *, func2(3, 2, k)
- ! A pure function is a function that doesn't modify its input parameters
- ! or cause any side-effects.
+ ! A pure function is a function that doesn't modify its input
+ ! parameters or cause any side-effects.
m = func3(3, 2, k)
-contains ! Zone for defining sub-programs internal to the program.
+contains ! Start defining the program's internal procedures:
! Fortran has a couple of slightly different ways to define functions.
integer function func(a, b, c) ! a function returning an integer value.
- ! implicit none ! subvariable fields can no longer declare implicit none
- integer, intent(in) :: a, b, c ! type of input parameters defined inside the function.
+ ! implicit none ! - no longer used in subvariable fields
+ integer, intent(in) :: a, b, c ! type of input parameters
+ ! the return variable defaults to the function name.
if (a >= 2) then
- func = a + b + c ! the return variable defaults to the function name.
- return ! can return the current value from the function at any time.
+ func = a + b + c
+ return ! returns the current value at 'func'
end if
func = a + c
@@ -286,24 +297,29 @@ contains ! Zone for defining sub-programs internal to the pro
integer, intent(in) :: a, b ! can declare and enforce that variables
!are not modified by the function.
integer, intent(inout) :: c
- integer :: f ! function return type declared inside the function.
- integer :: cnt = 0 ! GOTCHA - initialisation implies variable is
- !saved between function calls.
+ integer :: f
+ ! function return type declared inside the function.
+ integer :: cnt = 0 ! GOTCHA -
+ ! assigning a value at initalization
+ ! implies that the variable is
+ ! saved between function calls.
f = a + b - c
- c = 4 ! altering the value of an input variable.
+ c = 4 ! changing value of input variable c.
cnt = cnt + 1 ! count number of function calls.
end function func2
- pure function func3(a, b, c) ! a pure function can have no side-effects.
+ pure function func3(a, b, c) ! a pure function has no side-effects.
integer, intent(in) :: a, b, c
integer :: func3
func3 = a*b*c
end function func3
-
+
+ ! a subroutine does not return anything,
+ ! but can change the value of arguments.
subroutine routine(d, e, f)
real, intent(inout) :: f
real, intent(in) :: d, e
@@ -312,7 +328,8 @@ contains ! Zone for defining sub-programs internal to the pro
end subroutine routine
-end program example ! End of Program Definition -----------------------
+end program example
+! End of Program Definition -----------------------
! Functions and Subroutines declared externally to the program listing need
! to be declared to the program using an Interface declaration (even if they
@@ -350,7 +367,8 @@ module fruity
use fruit, only: apple, pear ! use apple and pear from fruit module.
implicit none ! comes after module imports.
- private ! make things private to the module (default is public).
+ ! By default all module data and functions will be public
+ private ! Instead set default to private
! Declare some variables/functions explicitly public.
public :: apple, mycar, create_mycar
! Declare some variables/functions private to the module (redundant here).