add defineFunction action

README.md

@@ -6,7 +6,7 @@
 
 **Heta** is a modeling language for quantitative systems pharmacology and systems biology.
 
-The current version is **0.4.2**.
+The current version is **0.4.3**.
 
 See also the [Heta video tutorial](https://hetalang.github.io/#/resources/?id=lesson-0-introduction)
 

actions.md

@@ -23,6 +23,7 @@ If no statement is written the default statement is `#upsert` which is the equiv
 - [export](#export)
 - [importNS](#importns)
 - [import](#import)
+- [defineFunction](#definefunction)
 
 ## insert
 
@@ -431,3 +432,35 @@ end
 | prefix | string | | "" | | prefix of new ids |
 | suffix | string | | "" | | suffix of new ids|
 | rename | Dictionary | | {} | | id matching table |
+
+## defineFunction
+
+_EXPERIMMENTAL_
+
+The `defineFunction` action allows users to write a simple function in the platform and use it together with pre-defined functions [from the list](math#list-of-functions).
+
+The `math` property of `defineFunction` may include arythmetic operators, pre-defined constants, identifiers of arguments, pre-defined functions and functions added with other `defineFunction` statements. It cannot include other identifiers like for components.
+
+| property | type | required | default | ref | description | 
+| ---------|------|----------|---------|-----|-------------|
+| id | `ID` | true | | | unique identifier of `FunctionDef` |
+| arguments | `ID[]` | | `[]` | | identifiers of arguments |
+| math | `string[]` | true | | | single string representing math expression |
+
+### Example 1
+
+```heta
+#defineFunction pow7 {
+  arguments: [x],
+  math: "pow(x, 7)"
+};
+```
+
+### Example 2
+
+```heta
+#defineFunction f3 {
+  arguments: [x1, x2, x3],
+  math: sqrt(x1^2 + x2^2 + x3^2)
+};
+```

changelog.md

@@ -1,5 +1,9 @@
 # Change Log
 
+## 0.4.3
+
+- add `#defineFunction` action as an experimental
+
 ## 0.4.2
 
 - use `import xxx.xlsx type table` instead of  `import xxx.xlsx type xlsx`