# Context

There are no global variables in the Gentee language. One of the ways to exchange data is a special associative array of strings (*context*). Any function can safely add key-value pairs there or get a value by key. In addition, the context has the ability to substitute other existing values from the context. For example, if the pairs *"a": "String A"* and *"b": "String B"* has been defined, then *"#a# and #b#"* will return *"String A and String B"*. The functions and operators for working with the context are described below.

* [Ctx( str input ) str](/stdlib/context.md#ctx-str-input-str)
* [CtxGet( str key ) str](/stdlib/context.md#ctxget-str-key-str)
* [CtxIs( str key ) bool](/stdlib/context.md#ctxis-str-key-bool)
* [CtxSet( str key, str val ) str](/stdlib/context.md#ctxset-str-key-str-val-str)
* [CtxSet( str key, bool b ) str](/stdlib/context.md#ctxset-str-key-bool-b-str)
* [CtxSet( str key, float f ) str](/stdlib/context.md#ctxset-str-key-float-f-str)
* [CtxSet( str key, int i ) str](/stdlib/context.md#ctxset-str-key-int-i-str)
* [CtxValue( str key ) str](/stdlib/context.md#ctxvalue-str-key-str)

## Operators

| Operator           | Result | Description                                                               |
| ------------------ | ------ | ------------------------------------------------------------------------- |
| **#** ident        | str    | The same as *CtxGet(key)*, where *ident* is the context key.              |
| **##** str         | str    | The same as *Ctx(str)*. Specify any expression that returns a string.     |
| ident **#=** str   | str    | The same as *CtxSet(str key, str s)*, where *ident* is the context key.   |
| ident **#=** bool  | str    | The same as *CtxSet(str key, bool b)*, where *ident* is the context key.  |
| ident **#=** float | str    | The same as *CtxSet(str key, float f)*, where *ident* is the context key. |
| ident **#=** int   | str    | The same as *CtxSet(str key, int i)*, where *ident* is the context key.   |

```go
run str {
  str s = ` #AºB#`
  AºB #= `ººº`
  b #= 71
  CD #= `#AºB# #b# == ` 
  return #CD + #b + ##s
}
// ººº 71 == 71 ººº
```

## Functions

### Ctx(str input) str

The *Ctx* function replaces substrings **#keyname#** in *input* string with the value of the corresponding key, if it exists.

```
run str {
    CtxSetBool(`qq`, true)
    CtxSetFloat(`ff`, 3.1415)
    CtxSet(`out`, "it is #qq# that PI equals #ff#")
    return Ctx("#out#. #notexist#")
}
// it is true that PI equals 3.1415. #notexist#
```

### CtxGet(str key) str

The *CtxGet* function gets the value of the *key* key, replaces all occurrences of other keys in it, and returns the resulting string. If the specified key is missing, an empty string is returned.

```
func init {
   CtxSet(`a1`, `end`)
   CtxSet(`a2`, `=#a1#=`)
   CtxSet(`a3`, `+#a2#+#a1#`)
}

run str {
    init()
    return CtxGet(`a3`)
}
// +=end=+end
```

### CtxIs(str key) bool

The *CtxIs* function returns *true* if there is a value with the specified key in the context. Otherwise, it returns *false*.

### CtxSet(str key, str val) str

The *CtxSet* function adds a key and a value to the context. If the key already exists, it will be assigned a new value. The function returns the value of the key.

### CtxSet(str key, bool b) str

The *CtxSet* function adds a key and a logical value *b* to the context. A boolean value will be converted to the string *true* or *false*. The function returns the value of the key.

### CtxSet(str key, float f) str

The *CtxSet* function adds a key and a floating-point number *f* to the context. The number will be converted to a string. The function returns the value of the key.

### CtxSet(str key, int i) str

The *CtxSet* function adds a key and an integer *i* to the context. The number will be converted to a string. The function returns the value of the key.

### CtxValue(str key) str

The *CtxValue* function returns the value of the *key* key as is. Unlike the **CtxGet** function, it does not replace occurrences of other keys. If the specified key is missing, an empty string is returned.

```
run str {
    CtxSet(`test`, `?value`)
    CtxSet(`param`, `#test# ==`)
    return CtxValue(`param`) + CtxValue(`nop`) + CtxGet(`param`)
}
// #test# ==?value ==
```


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