Pratt and Shunting-Yard Parsers for Configurable MQL5 Expressions

Summary

This article explains precedence-based approaches for parsing mathematical expressions in MQL, focusing on Pratt and shunting-yard parsers. It describes how operator precedence tables distinguish prefix symbols from infix operators, then outlines the Pratt parser’s recursive process: parse a prefix construct, and continue incorporating infix constructs while their precedence permits. Parentheses, unary operators, identifiers, and numeric values are handled as expression components.

The article places these methods in a broader implementation that lets users express signal logic through configurable expressions and connect the resulting evaluations to trading actions. It presents parsers as a programming tool for embedding editable rules in an Expert Advisor, not as a source of profitable signals. The text says a sample EA may trade poorly in the Strategy Tester and cautions that parsers themselves do not provide ready-made profitable systems. Its value is mainly in software design and strategy configuration; it does not offer comparative parser benchmarks or trading-performance evidence.

Key ideas

• Precedence tables let parsers determine how operators group when parentheses are absent.
• The Pratt method parses prefix constructs first, then consumes infix constructs according to precedence.
• The article also examines the shunting-yard method as an alternative precedence-based parser.
• Expression parsing can let users configure signal logic without editing core MQL code.
• A parser is an implementation tool and does not itself establish a profitable trading strategy.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.