documented clip function in newly created stdlib_math.md file

Author: aman-godara

doc/specs/stdlib_math.md

@@ -0,0 +1,101 @@
+---
+title: math
+---
+
+# The `stdlib_math` module
+
+[TOC]
+
+## Introduction
+
+`stdlib_math` module provides with general purpose mathematical functions.
+
+
+## Procedures and Methods provided
+
+
+<!-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -->
+### `clip` function
+
+#### Description
+
+Limits the input value `x` to the given interval [`xmin`, `xmax`] (interval is `xmin` and `xmax` inclusive). Returns a value which lies in the given interval and is closest to the input value `x`.  
+If the input value `x` already lies in the given interval, then the output value will be equal to the input value.
+
+Note: A valid input must **NOT** have `xmin` value greater than `xmax` value.
+
+#### Syntax
+
+`res = [[stdlib_math(module):clip(interface)]] (x, xmin, xmax)`
+
+#### Status
+
+Experimental
+
+#### Class
+
+Elemental function.
+
+#### Argument(s)
+
+`x`: scalar of either `integer` or `real`. This argument is `intent(in)`.  
+`xmin`: scalar of either `integer` or `real`. This argument is `intent(in)`.  
+`xmax`: scalar of either `integer` or `real`. This argument is `intent(in)`.
+
+Note: All arguments must have same `type` and same `kind`.
+
+#### Output value or Result value
+
+Output is a scalar of either `integer` or `real` depending on the arguments. The output value will have `type` and `kind` same as to that of the arguments.
+
+#### Example(s) of usage
+
+##### Example 1:
+
+Here inputs are of type `integer` and kind `int32`
+```fortran
+program demo
+  use stdlib_math
+  use iso_fortran_env
+  implicit none
+  integer(int32) :: x
+  integer(int32) :: xmin
+  integer(int32) :: xmax
+  integer(int32) :: clipped_value
+
+  xmin = -5
+  ! xmin <- -5
+  xmax = 5
+  ! xmax <- 5
+  x = 12
+  ! x <- 12
+
+  clipped_value = clip(x, xmin, xmax)
+  ! clipped_value <- 5
+end program demo
+```
+
+##### Example 2:
+
+Here inputs are of type `real` and kind `real32` (or `sp`)
+```fortran
+program demo
+  use stdlib_math
+  use iso_fortran_env
+  implicit none
+  real(real32) :: x
+  real(real32) :: xmin
+  real(real32) :: xmax
+  real(real32) :: clipped_value
+
+  xmin = -5.76999998
+  ! xmin <- -5.76999998
+  xmax = 3.02500010
+  ! xmax <- 3.02500010
+  x = 3.02500010
+  ! x <- 3.02500010
+
+  clipped_value = clip(x, xmin, xmax)
+  ! clipped_value <- 3.02500010
+end program demo
+```