Migrating MQL4 Indicators and Scripts to MQL5
Summary
This document explains how to adapt many MQL4 scripts, indicators, libraries, and other non-trading code for use in MQL5. It covers replacing legacy event functions with MQL5 handlers, adjusting indicator properties and input parameters, and renaming conflicting functions to compatibility wrappers. It also describes initializing MQL4-style reserved variables and points users to the corresponding functions in the library.
The library does not implement expert-advisor order submission or trade management, so trading logic still needs to be rewritten. Some functions are stubs that return an error value, and indicators may need manual changes to initialization and property declarations. The document provides migration instructions and function examples, but no performance tests or evidence that converted trading systems behave identically. It is therefore a platform-porting reference rather than guidance on a trading strategy.
Key ideas
- The compatibility library supports many MQL4 functions in MQL5, but does not handle expert-advisor trading mechanics.
- Legacy initialization and execution handlers must be converted to the corresponding MQL5 event functions.
- Conflicting functions can be accessed through compatibility versions with modified names.
- MQL5 indicator inputs are constants, so code that changes them needs temporary variables instead.
- Some library functions are stubs, and converted programs may require additional manual edits.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.