02 Language Evaluation

Qualities of a Language¶

Features¶

Simplicity¶

Fewer features and basic constructs¶

The main cause of readability issues is because program author uses a subset different from what the reader is familiar with

Fewer Feature Multiplicity¶

Feature Multiplicity = Ability to do the same operation in different ways

count = count + 1;
count += 1;
count++;
++count;

Fewer Operator Overloading¶

Ambiguity arises due to ability of operator to perform multiple operations

Orthogonality¶

Constructs in programming languages should be independent of each other; should not be redundant. Every combination of features should be meaningful.

Any operation has minimal undesired side effects.

Orthogonality is the property that means "Changing A does not change B".

An example of an orthogonal system would be a radio, where changing the station does not change the volume and vice-versa.

A non-orthogonal system would be like a helicopter where changing the speed can change the direction.

In programming languages this means that when you execute an instruction, nothing but that instruction happens (which is very important for debugging).

Data Types & Structures¶

For eg, the existence of boolean data type in a programming language is important, as otherwise we have to use integers (which make the program less clear)

Syntax Design¶

Identifiers¶

Names for variables, functions, arrays, structures, etc

Rules¶

• Starting character must be alphabet/underscore
• Other characters can be
  • Alphabet
  • Underscore
  • Digits
• Max Length = 31 characters

Key Words¶

while, for, class

Most programming languages use braces for pairing control structers

Semantics should follow Syntax¶

Semantics = meaning of your code; basically the logic

For eg, use of static, extern in C

Form and Meaning¶

Self-descriptive constructs and meaningful keywords

Abstraction¶

Ability to define and use complex structures/operations in ways that allow details to be ignored

Process Abstraction¶

Functions/Sub-routines for codes that will be required multiple times

Data Abstraction¶

Ability to create own data structures, such as binary tree using pointers/integers

Expressivity¶

Set of relatively convenient ways of specifying operations

Examples¶

• count++ instead of count = count + 1
• for instead of while

Type Checking¶

Testing for type errors - ensuring that operands of an operator are of compatible type

Run-Time type checking is expensive, hence compile-time type checking is preferred

Exception Handling¶

Intercept run-time errors and take corrective measures

Restricted Aliasing¶

Aliasing = Presence of multiple names for the same memory location

Changing value pointed by one pointer changes the value pointed by another pointer to the same location.

❌ In C, union members and pointers may be set to point to the same variable.

Grep¶

**G**et **re**gular **e**x**p**ression

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