program main

!*****************************************************************************80
!
!! DISLIN_EX14 demonstrates the use of TeX instructions for math formulas.
!
!  Discussion:
!
!    On Unix systems, the backslash character is interpreted as a special
!    symbol BEFORE THE COMPILER SEES IT, unless it is inside a double-quote
!    string.
!
!    If you know the program will be used on a UNIX system, you can 'simply'
!    type TWO backslash characters whenever you mean one.
!
!    This is all because of the painful legacy of poorly thought out and
!    inconsistent escape character systems.
!
!  Modified:
!
!    05 September 2005
!
  use dislin

  implicit none

  character ( len = 80 ) :: cstr
  integer :: nl

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'DISLIN_EX14:'
  write ( *, '(a)' ) '  FORTRAN90 version'
  write ( *, '(a)' ) '  Demonstrate the use of TeX instructions to'
  write ( *, '(a)' ) '  create mathematical formulas.'
!
!  Specify the format of the output file.
!
  call metafl ( 'PNG' )
!
!  Specify the name of the output graphics file.
!
  call setfil ( 'dislin_ex14.png' )
!
!  Set up the plot.
!
  call setpag ( 'da4p' )
  call disini ( )
  call pagera ( )
  call complx ( )
  call height ( 40 )

  cstr = 'TeX instructions for mathematical formulas'
  nl = nlmess ( cstr )
  call messag ( cstr, (2100 - nl)/2, 100 )

  call texmod ( 'on' )
  call messag ( '$\frac{1}{x+y}$', 150, 400 )
  call messag ( '$\frac{a^2 - b^2}{a+b} = a - b$', 1200, 400 )

  call messag ( '$r = \sqrt{x^2 + y^2}', 150, 700 )
  call messag ( '$\cos \phi = \frac{x}{\sqrt{x^2 + y^2}}$', 1200, 700 )

  call messag ( '$\gamma(x) = \int_0^\infty e^{-t}t^{x-1}dt$', 150, 1000 )
  call messag ( '$\lim_{x \to \infty} (1 + \frac{1}{x})^x = e$', 1200, 1000 )

  call messag ( '$\mu = \sum_{i=1}^n x_i p_i$', 150, 1300 )
  call messag ( '$\mu = \int_{-\infty}^ \infty x f(x) dx$', 1200, 1300 )

  call messag ( '$\overline{x} = \frac{1}{n} \sum_{i=1}^n x_i$', 150, 1600 )
  call messag ( '$s^2 = \frac{1}{n-1} \sum_{i=1}^n (x_i - \overline{x})^2$', &
    1200, 1600 )

  call messag ( '$\sqrt[n]{\frac{x^n - y^n}{1 + u^{2n}}}$', 150, 1900 )
  call messag ( '$\sqrt[3]{-q + \sqrt{q^2 + p^3}}$', 1200, 1900 )

  call messag ( '$\int \frac{dx}{1+x^2} = \arctan x + c$', 150, 2200)
  call messag ( '$\int \frac{dx}{\sqrt{1+x^2}} = {\rm arsinh} x + c$', &
    1200, 2200 )

  call messag ( '$\overline{p_1p_2} = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}$', &
    150, 2500 )
  call messag ( '$x = \frac{x_1 + \lambda x_2}{1 + \lambda}$', 1200, 2500 )

  call disfin ( )

  write ( *, '(a)' ) ' '
  write ( *, '(a)' ) 'DISLIN_EX14:'
  write ( *, '(a)' ) '  Normal end of execution.'

  stop
end