FParsec vs alternatives

The following tables contain a bullet‐point comparison between FParsec and the two main alternatives for parsing with F#: parser generator tools (e.g. fslex & fsyacc) and “hand‐written” recursive descent parsers.

Table 1.1.1: Relative advantages
Parser‐generator tools	FParsec	Hand‐written recursive‐descent parser
Declarative and easy‐to‐read syntax Ensures adherence to grammar formalism Can check for certain kinds of ambiguity in grammar You don’t have to think about performance. Either the generated parser is fast enough, or not. There’s not much you can do about it.	Implemented as F# library, so no extra tools or build steps Parsers are first‐class values within the language Succinct and expressive syntax Modular and easily extensible Extensive set of predefined parsers and combinators Semi‐automatically generated, highly readable error messages Supports arbitrary lookahead and backtracking Runtime‐configurable operator‐precedence parser component Does not require a pre‐parsing tokenization phase Comprehensive documentation Extensively unit‐tested	No extra tools or build steps Most amenable to individual requirements Potentially as fast as technically possible Parsers are relatively portable if you stick to simple language features and keep library dependencies to a minimum

Table 1.1.2: Relative disadvantages
Parser‐generator tools	FParsec	Hand‐written recursive‐descent parser
Restricted to features of grammar formalism Extra tools and compilation steps Reliance on opaque generator tool, that is often hard to debug, optimize or extend Static grammar that can’t be changed at runtime Often hard to generate good error messages Many tools generate comparatively slow parsers Some tools have only limited Unicode support Portability problems	Tradeoff between declarativeness and performance Syntax less readable than PEG or Regular Expression syntax Left‐recursive grammar rules have to be rewritten Does not support a pre‐parsing tokenization phase You have to learn the API Limited to F# Code‐dependence on FParsec Aggressive performance optimizations add complexity to parts of the lower‐level FParsec source code	You have to write everything yourself, which can take a lot of effort Implementing (fast) parsers requires some experience Expression (sub)grammars with infix operators can be ugly and inefficient to parse with a pure recursive‐descent parser, so you might also have to write some kind of embedded operator precedence parser

1.1 FParsec vs alternatives