What Is An Abstract Syntax Tree

Abstract syntax


Syntax in computer programming means the rules that control the structure of the symbols, punctuation, and words of a programming language. … For example, a series of English words, such as — subject a need and does sentence a verb — has little meaning without syntax

In computer science, the syntax of a computer language is the set of rules that defines the combinations of symbols that are considered to be correctly structured statements or expressions in that language.


  • Prolog syntax and semantics.
  • Perl syntax.
  • PHP syntax and semantics.
  • syntax.
  • C++ syntax.
  • Java syntax.
  • JavaScript syntax.
  • Python syntax and semantics.

Syntax Examples

One way to explore syntax is to know your clauses. There are independent and dependent clauses An independent clause is one that can stand alone and form a complete sentence. A dependent clause, however, cannot stand on its own.

For example, “Hurrying to the door, she picked up her purse and ran.” In this sentence, “hurrying to the door” is the dependent clause and “she picked up her purse and ran” is the independent clause. Let’s take a look at these clauses becoming full sentences with the right syntax.

Simple Sentences

Remember our basic construct of subject + verb + direct object? These are called simple sentences It’s a nice way to start when you’re just learning the English language. There’s the subject (person or thing being discussed), verb (action-giver), and direct object (receiving the action of the verb). Here are some examples:

  • I enjoy college.
  • Work pays the bills.
  • Hurricanes are scary.
  • The sky is pink.
  • The dog loves her owner.

The syntax in these lines is fine. They’re grammatically correct. But, what if we could dazzle up our syntax a little? Let’s take a look at a more detailed construct.

Complex Sentences

One of the best ways to improve our syntax is to move beyond the simple sentence. This brings us to complex sentences These are sentences that contain a subordinate clause. A subordinate clause is an additional bit of information. This means complex sentences come together by combining a dependent clause (incomplete sentence/subordinate clause) and an independent clause (complete thought).

Let’s expand the simple sentences above to create a new kind of syntax:

  • Even though it’s ridiculously expensive, I enjoy college.
  • Work pays the bills, whether you like it or not.
  • In the south of Florida, hurricanes are scary.
  • The sky is pink, especially in the romantic city of Paris.
  • Ever since she rescued her, the dog loves her owner.


How to Improve Syntax in Your Writing

Of course, the syntax of a sentence is more than the addition of a clause or two. How could it be that easy when the English language has so many rules (and exceptions)? On that note, it’s important to note the difference between syntax and grammar.

Grammar is the rulebook Grammar tells us to punctuate a sentence, capitalize proper nouns, and so forth. Syntax, however, is the application of the rules. It’s how we combine all those rules to compose clear constructs. Here are three ways to improve the syntax in your writing.

1. Use the Active Voice

One of the best ways to keep your syntax clear is to write in the active voice This means the subject is carrying out the action of the sentence. The active voice avoids muddled language. For example:

Hiking up the Andes, he drinks a bottle of water.

This line is written in the present tense using the active voice. That’s good. What you want to avoid is something like this:

Hiking up the Andes, a bottle of water is drunk by him.

In addition to the unnecessary awkwardness of the passive voice, this sentence also implies that the bottle of water was one doing the hiking. Applying the rules of voice to your syntax allows you to write in a clear and present tense, free from an excess of helping verbs.

2. Match Your Numbers

This refers to your use of singular and plural words If your subject is plural, then the rest of your sentence should be too. The same goes for singular instances. Let’s take a look:

The club members love riding their bikes together.

Here, we have a plural subject that matches its verb. You wouldn’t write:

The club members loves riding their bikes together.

You also wouldn’t write:

The club member love riding his bike.

In these examples, you can see how syntax is the application of the rules. The rules tell us the difference between singular and plural words. Syntax allows us to apply them with clarity and precision.Advertisement

3. Avoid Repetition

In an effort to be clear, we sometimes tiptoe around redundancy. For example, you wouldn’t want to write:

Due to his overwhelming fear, he frightfully tethered the ship to the post.

When trying to paint a picture for a reader, it can be tempting to overemphasize. But, proper syntax allows us to paint a vivid scene with our clauses, numbers, and active voice. The line above can be transformed into something like:

Overwhelming fear complicated the simple task of tethering his boat to the dock.

Of course, this sentence can be re-written in many different ways. Therein lies the beauty of syntax. It allows us to apply the rules, find our own voice, and engage readers in our own unique way.


In computer science, the abstract syntax of data is its structure described as a data type, independent of any particular representation or encoding. This is particularly used in the representation of text in computer languages, which are generally stored in a tree structure as an abstract syntax tree.


n computer science, an abstract syntax tree, or just syntax tree, is a tree representation of the abstract syntactic structure of source code written in a programming language. Each node of the tree denotes a construct occurring in the source code.

An abstract syntax tree (AST) is a way of representing the syntax of a programming language as a hierarchical tree-like structure. This structure is used for generating symbol tables for compilers and later code generation. The tree represents all of the constructs in the language and their subsequent rules.

An abstract syntax tree represents all of the syntactical elements of a programming language, similar to syntax trees that linguists use for human languages. The tree focuses on the rules rather than elements like braces or semicolons that terminate statements in some languages. The tree is hierarchical, with the elements of programming statements broken down into their parts. For example, a tree for a conditional statement has the rules for variables hanging down from the required operator.

ASTs are widely used in compilers to check code for accuracy. If the generated tree contains errors, the compiler prints an error message. ASTs are used because some constructs cannot be represented in a context-free grammar, such as implicit typing. ASTs are highly specific to programming languages, but research is underway on universal syntax trees.

What is the difference between abstract syntax and concrete syntax?

The abstract syntax is part of the definition of a particular implementation (evaluator or compiler) of a language. … The concrete syntax of a programming language is defined by a context free grammar. It consists of a set of rules (productions) that define the way programs look like to the programmer.

What is the advantage of syntax tree?

The advantages of using parse trees instead of semantic actions: You can make multiple passes over the data without having to re-parse the input. You can perform transformations on the tree. You can evaluate things in any order you want, whereas with attribute schemes you have to process in a begin to end fashion.

Drop your comment


Author: refuge_2020

Leave a Reply

Your email address will not be published. Required fields are marked *