# Let's Build A Simple Interpreter. Part 3.

DevFeed: [Let's Build A Simple Interpreter. Part 3.](<https://devfeed.tech/articles/let-s-build-a-simple-interpreter-part-3-33324.md>)

Original publisher: [Read original article](<https://ruslanspivak.com/lsbasi-part3/>)

Author: Ruslan Spivak

Published: 2015-08-12T11:00:00Z

Content type: tutorial

Language: en

Sources: [Ruslan Spivak](<https://devfeed.tech/sources/ruslan-spivak.md>)

Topics: [Parser](<https://devfeed.tech/topics/parser.md>), [Programming language](<https://devfeed.tech/topics/programming-language.md>), [syntax](<https://devfeed.tech/topics/syntax.md>), [Programming](<https://devfeed.tech/topics/programming.md>)

Tags: [blog](<https://devfeed.tech/tags/blog.md>), [how-to](<https://devfeed.tech/tags/how-to.md>), [parsing](<https://devfeed.tech/tags/parsing.md>), [programming-language](<https://devfeed.tech/tags/programming-language.md>), [syntax](<https://devfeed.tech/tags/syntax.md>)

## AI overview

Part 3 of a series on building a simple interpreter explains how to parse and interpret arithmetic expressions containing any number of plus or minus operators. It introduces syntax diagrams as visual representations of programming-language grammar and shows how they can guide parser implementation.

## Source excerpt

I woke up this morning and I thought to myself: "Why do we find it so difficult to learn a new skill?" I don't think it's just because of the hard work. I think that one of the reasons might be that we spend a lot of time ...