Add docs for type helpers

Author: aedart

docs/+current/modules/helpers/types.md

@@ -0,0 +1,180 @@
+---
+title: Types
+description: How to use the helpers module.
+keywords: helpers, cmake
+author: RSP Systems A/S
+---
+
+# Type Utilities
+
+The following helper functions can help you distinguish between the value type¹ of variables.
+
+¹: _In CMake all variable values are strings. See [official documentation](https://cmake.org/cmake/help/latest/manual/cmake-language.7.html#variables) for details._
+
+[TOC]
+
+## `is_int`
+
+Determines if value is an integer.
+
+```cmake
+is_int(22 a)
+is_int("hi there" b)
+
+message("${a}") # true
+message("${b}") # false
+```
+
+## `is_float`
+
+Determines if value is a float point.
+
+```cmake
+is_float(2.34 a)
+is_float(2 b)
+is_int("hi there" c)
+
+message("${a}") # true
+message("${b}") # false
+message("${c}") # false
+```
+
+## `is_numeric`
+
+Determines if value is numeric.
+
+```cmake
+is_numeric(22 a)
+is_numeric(1.234 b)
+is_numeric("hi there" c)
+
+message("${a}") # true
+message("${b}") # true
+message("${c}") # false
+```
+
+## `is_bool`
+
+Determines if value is a boolean (_`true` or `false`_).
+
+```cmake
+is_bool(true a)
+is_bool(false b)
+is_bool("on" c)
+
+message("${a}") # true
+message("${b}") # true
+message("${c}") # false
+```
+
+## `is_bool_like`
+
+Determine if value is a boolean like.
+See CMake's official documentation for additional details:
+
+* [constant](https://cmake.org/cmake/help/latest/command/if.html#constant)
+* [logic operators](https://cmake.org/cmake/help/latest/command/if.html#logic-operators)
+
+
+```cmake
+is_bool_like(true a)
+is_bool_like("yes" b)
+is_bool_like(-2 c)
+
+message("${a}") # true
+message("${b}") # true
+message("${c}") # false
+```
+
+## `is_list`
+
+Determines if value is a list of values.
+See CMake's official [documentation](https://cmake.org/cmake/help/latest/manual/cmake-language.7.html#cmake-language-lists)
+for additional details.
+
+```cmake
+is_list("aa;bbb;ccc" a)
+
+set(my_list "aa;bbb;ccc")
+is_list(my_list b)
+
+set(my_other_list aa bbb ccc)
+is_list(my_other_list c)
+
+is_list("aa bbb ccc" d)
+
+message("${a}") # true
+message("${b}") # true
+message("${c}") # true
+message("${d}") # false
+```
+
+## `is_command`
+
+Determines if value is command, [macro](https://cmake.org/cmake/help/latest/command/macro.html#macro) or
+[function](https://cmake.org/cmake/help/latest/command/function.html#command:function).
+
+```cmake
+macro(my_macro)
+endmacro()
+is_command(my_macro a)
+
+function(my_function)
+endfunction()
+is_command(my_function b)
+
+set(my_var "")
+is_command(my_var c)
+
+message("${a}") # true
+message("${b}") # true
+message("${c}") # false
+```
+
+## `is_string`
+
+Determines if value is a string.
+In this context, a value is considered to be a string, if it is:
+
+* not [numeric](#is_numeric)
+* not [boolean](#is_bool) (_`true` or `false`_)
+* not a [list](#is_list) (_semicolon separated list_)
+* not a [command](#is_command)
+
+```cmake
+is_string("abc" a)
+
+set(my_str "foo")
+is_string(my_str b)
+
+is_string(42 c)
+
+message("${a}") # true
+message("${b}") # true
+message("${c}") # false
+```
+
+## `get_type`
+
+Determines the type of given value.
+Function assigns a string representation of the value's type (_int, float, bool, list, command, or string_), to
+the `output` argument.
+
+* See [`is_int()`](#is_int)
+* See [`is_float()`](#is_float)
+* See [`is_bool()`](#is_bool)
+* See [`is_list()`](#is_list)
+* See [`is_command()`](#is_command)
+* See [`is_string()`](#is_string)
+
+```cmake
+get_type("abc" a)
+get_type("aaa;bbb;ccc" b)
+get_type(true c)
+get_type(12 d)
+
+message("${a}") # string
+message("${b}") # list
+message("${c}") # bool
+message("${c}") # int
+```