Documented support for `is in`, added support for `is not in`. (#955)

* Documented support for `is in`, added support for `is not in`.
Fixes #937
* minor docs improvement

3 files changed, 28 insertions, 51 deletions

diff --git a/docs/designers/language-basic-syntax/language-syntax-operators.md b/docs/designers/language-basic-syntax/language-syntax-operators.md
index 98eff076..98a56538 100644
--- a/docs/designers/language-basic-syntax/language-syntax-operators.md
+++ b/docs/designers/language-basic-syntax/language-syntax-operators.md
@@ -27,6 +27,30 @@ Various basic operators can be applied directly to variable values.
 > complex, it may be a good idea to move the bits that do not deal
 > explicitly with presentation to PHP by way of plugins or modifiers.
 
+## List
+The following is a list of recognized operators, which must be
+separated from surrounding elements by spaces. Note that items listed in
+\[brackets\] are optional. PHP equivalents are shown where applicable.
+
+| Operator           | Alternates | Syntax Example       | Meaning                        | PHP Equivalent     |
+|--------------------|------------|----------------------|--------------------------------|--------------------|
+| ==                 | eq         | $a eq $b             | equals                         | ==                 |
+| !=                 | ne, neq    | $a neq $b            | not equals                     | !=                 |
+| >                  | gt         | $a gt $b             | greater than                   | >                  |
+| <                  | lt         | $a lt $b             | less than                      | <                  |
+| >=                 | gte, ge    | $a ge $b             | greater than or equal          | >=                 |
+| <=                 | lte, le    | $a le $b             | less than or equal             | <=                 |
+| ===                |            | $a === 0             | check for identity             | ===                |
+| !                  | not        | not $a               | negation (unary)               | !                  |
+| %                  | mod        | $a mod $b            | modulo                         | %                  |
+| is \[not\] div by  |            | $a is not div by 4   | divisible by                   | $a % $b == 0       |
+| is \[not\] even    |            | $a is not even       | \[not\] an even number (unary) | $a % 2 == 0        |
+| is \[not\] even by |            | $a is not even by $b | grouping level \[not\] even    | ($a / $b) % 2 == 0 |
+| is \[not\] odd     |            | $a is not odd        | \[not\] an odd number (unary)  | $a % 2 != 0        |
+| is \[not\] odd by  |            | $a is not odd by $b  | \[not\] an odd grouping        | ($a / $b) % 2 != 0 |
+| is in              |            | $a is in $b          | exists in array                | in_array($a, $b)   |
+| is \[not\] in      |            | $a is not in $b      | does not exist in array        | !in_array($a, $b)  |
+
 ## Ternary
 You can use the `?:` (or ternary) operator to test one expression and present the value
 of the second or third expression, based on the result of the test.
diff --git a/docs/designers/language-builtin-functions/language-function-if.md b/docs/designers/language-builtin-functions/language-function-if.md
index 1372ea58..eb00cfda 100644
--- a/docs/designers/language-builtin-functions/language-function-if.md
+++ b/docs/designers/language-builtin-functions/language-function-if.md
@@ -3,32 +3,8 @@
 `{if}` statements in Smarty have much the same flexibility as PHP
 [if](https://www.php.net/if) statements, with a few added features for the
 template engine. Every `{if}` must be paired with a matching `{/if}`.
-`{else}` and `{elseif}` are also permitted. All PHP conditionals and
-functions are recognized, such as *\|\|*, *or*, *&&*, *and*,
-*is_array()*, etc.
-
-The following is a list of recognized qualifiers, which must be
-separated from surrounding elements by spaces. Note that items listed in
-\[brackets\] are optional. PHP equivalents are shown where applicable.
-
-## Qualifiers
-
-| Qualifier          | Alternates | Syntax Example       | Meaning                        | PHP Equivalent     |
-|--------------------|------------|----------------------|--------------------------------|--------------------|
-| ==                 | eq         | $a eq $b             | equals                         | ==                 |
-| !=                 | ne, neq    | $a neq $b            | not equals                     | !=                 |
-| >                  | gt         | $a gt $b             | greater than                   | >                  |
-| <                  | lt         | $a lt $b             | less than                      | <                  |
-| >=                 | gte, ge    | $a ge $b             | greater than or equal          | >=                 |
-| <=                 | lte, le    | $a le $b             | less than or equal             | <=                 |
-| ===                |            | $a === 0             | check for identity             | ===                |
-| !                  | not        | not $a               | negation (unary)               | !                  |
-| %                  | mod        | $a mod $b            | modulo                         | %                  |
-| is \[not\] div by  |            | $a is not div by 4   | divisible by                   | $a % $b == 0       |
-| is \[not\] even    |            | $a is not even       | \[not\] an even number (unary) | $a % 2 == 0        |
-| is \[not\] even by |            | $a is not even by $b | grouping level \[not\] even    | ($a / $b) % 2 == 0 |
-| is \[not\] odd     |            | $a is not odd        | \[not\] an odd number (unary)  | $a % 2 != 0        |
-| is \[not\] odd by  |            | $a is not odd by $b  | \[not\] an odd grouping        | ($a / $b) % 2 != 0 |
+`{else}` and `{elseif}` are also permitted. All [operators](../language-basic-syntax/language-syntax-operators.md) are recognized, such as *==*,
+*\|\|*, *or*, *&&*, *and*, etc and you can use modifiers as functions, such as *is_array()*.
 
 ## Examples
 ```smarty
diff --git a/docs/designers/language-builtin-functions/language-function-while.md b/docs/designers/language-builtin-functions/language-function-while.md
index 13eaef9b..d0a4b2f3 100644
--- a/docs/designers/language-builtin-functions/language-function-while.md
+++ b/docs/designers/language-builtin-functions/language-function-while.md
@@ -3,31 +3,8 @@
 `{while}` loops in Smarty have much the same flexibility as PHP
 [while](https://www.php.net/while) statements, with a few added features for
 the template engine. Every `{while}` must be paired with a matching
-`{/while}`. All PHP conditionals and functions are recognized, such as
-*\|\|*, *or*, *&&*, *and*, *is_array()*, etc.
-
-The following is a list of recognized qualifiers, which must be
-separated from surrounding elements by spaces. Note that items listed in
-\[brackets\] are optional. PHP equivalents are shown where applicable.
-
-## Qualifiers
-
-| Qualifier          | Alternates | Syntax Example       | Meaning                        | PHP Equivalent     |
-|--------------------|------------|----------------------|--------------------------------|--------------------|
-| ==                 | eq         | $a eq $b             | equals                         | ==                 |
-| !=                 | ne, neq    | $a neq $b            | not equals                     | !=                 |
-| >                  | gt         | $a gt $b             | greater than                   | >                  |
-| <                  | lt         | $a lt $b             | less than                      | <                  |
-| >=                 | gte, ge    | $a ge $b             | greater than or equal          | >=                 |
-| <=                 | lte, le    | $a le $b             | less than or equal             | <=                 |
-| ===                |            | $a === 0             | check for identity             | ===                |
-| !                  | not        | not $a               | negation (unary)               | !                  |
-| %                  | mod        | $a mod $b            | modulo                         | %                  |
-| is \[not\] div by  |            | $a is not div by 4   | divisible by                   | $a % $b == 0       |
-| is \[not\] even    |            | $a is not even       | \[not\] an even number (unary) | $a % 2 == 0        |
-| is \[not\] even by |            | $a is not even by $b | grouping level \[not\] even    | ($a / $b) % 2 == 0 |
-| is \[not\] odd     |            | $a is not odd        | \[not\] an odd number (unary)  | $a % 2 != 0        |
-| is \[not\] odd by  |            | $a is not odd by $b  | \[not\] an odd grouping        | ($a / $b) % 2 != 0 |
+`{/while}`. All [operators](../language-basic-syntax/language-syntax-operators.md) are recognized, such as *==*,
+*\|\|*, *or*, *&&*, *and*, etc and you can use modifiers as functions, such as *is_array()*.
 
 ## Examples
 ```smarty