Improve documentation of builtin functions

Relates to #38

Author: ISibboI

Cargo.lock

@@ -214,16 +214,9 @@ This crate offers a set of builtin functions.
 |------------|-----------------|-------------|
 | min | >= 1 | Returns the minimum of the arguments |
 | max | >= 1 | Returns the maximum of the arguments |
-| len | 1 | Return the character length of string argument |
-| str::regex_matches | 2 | Returns true if first string argument matches regex in second |
-| str::regex_replace | 3 | Returns string with matches replaced by third argument |
-| str::to_lowercase | 1 | Returns lower-case version of string |
-| str::to_uppercase | 1 | Returns upper-case version of string |
-| str::trim | 1 | Strips whitespace from start and end of string |
 
 The `min` and `max` functions can deal with a mixture of integer and floating point arguments.
-They return the result as the type it was passed into the function. The regex functions require
-feature flag `regex_support`.
+They return the result as the type it was passed into the function.
 
 ### Values
 

README.md

@@ -120,7 +120,7 @@
 //! | * | 100 | Product |
 //! | / | 100 | Division |
 //! | % | 100 | Modulo |
-//! | + | 95 | Sum |
+//! | + | 95 | Sum or String Concatenation |
 //! | - | 95 | Difference |
 //! | < | 80 | Lower than |
 //! | \> | 80 | Greater than |
@@ -197,13 +197,22 @@
 //!
 //! This crate offers a set of builtin functions.
 //!
-//! | Identifier | Argument Amount | Description |
-//! |------------|-----------------|-------------|
-//! | min | >= 1 | Returns the minimum of the arguments |
-//! | max | >= 1 | Returns the maximum of the arguments |
+//! | Identifier | Argument Amount | Argument Types | Description |
+//! |------------|-----------------|----------------|-------------|
+//! | `min` | >= 1 | Numeric | Returns the minimum of the arguments |
+//! | `max` | >= 1 | Numeric | Returns the maximum of the arguments |
+//! | `len` | 1 | String | Returns the character length of a string |
+//! | `str::regex_matches` | 2 | String, String | Returns true if the first argument matches the regex in the second argument |
+//! | `str::regex_replace` | 3 | String, String, String | Returns the first argument with all matches of the regex in the second argument replaced by the third argument |
+//! | `str::to_lowercase` | 1 | String | Returns the lower-case version of the string |
+//! | `str::to_uppercase` | 1 | String | Returns the upper-case version of the string |
+//! | `str::trim` | 1 | String | Strips whitespace from the start and the end of the string |
 //!
 //! The `min` and `max` functions can deal with a mixture of integer and floating point arguments.
-//! They return the result as the type it was passed into the function.
+//! If the maximum or minimum is an integer, then an integer is returned.
+//! Otherwise, a float is returned.
+//!
+//! The regex functions require the feature flag `regex_support`.
 //!
 //! ### Values
 //!