Hope (programming language) facts for kids

Hope is a special kind of programming language that was created in the 1970s. It was developed by smart people at the University of Edinburgh in Scotland.

Hope is known as a functional programming language. This means it works by using functions, a bit like math equations. It was one of the first languages to have cool features like "call-by-pattern evaluation" and "algebraic data types." These are ways the language handles information and solves problems.

Hope came before some well-known languages you might hear about today, like Haskell. It was developed around the same time as another language called ML. Hope was inspired by an even simpler language called NPL, created by Rod Burstall and John Darlington.

Why is it called Hope?

The language was named after a person! It's named after Sir Thomas Hope (around 1681–1771). He was a Scottish farmer who helped improve farming methods.

The place where Hope was created, the Department of Artificial Intelligence in Edinburgh, was located near a spot called Hope Park Square. This square was also named after Sir Thomas Hope. So, the language got its name from this historical connection.

How Hope Works

Hope is a unique language with specific rules.

Writing Programs in Hope

In Hope, you write programs using special rules. For example, here is how you might tell Hope to calculate a factorial number: dec fact : num -> num; --- fact 0 <= 1; --- fact n <= n*fact(n-1);

This code tells the computer how to figure out the factorial of any number. The order of these instructions doesn't change how the program works. This is because Hope uses something called "pattern matching." It always picks the most exact rule first.

Types and Data

In Hope, you always have to tell the computer what kind of information you are using. This is called "explicit type declarations." For example, you have to say if a number is a whole number or a decimal. Hope does not guess the type for you.

Hope also has two basic ways to organize information:

• Tuples: These are like fixed lists of different types of items. Imagine a box that always holds a name and an age.
• Lists: These are like flexible lists that can hold many items of the same type. Think of a shopping list.

Versions of Hope

Over the years, different versions of Hope have been created.

The very first version of Hope worked in a "strict" way. This means it would do every calculation right away. Later, some versions were made to work in a "lazy" way. This means they would only do a calculation when it was absolutely needed.

A company called British Telecom worked with Imperial College to make a strict version of Hope. The first one was released in 1986.

A newer language called Hope+ was also developed. It was a joint project between Imperial College and ICL (International Computers Limited). Hope+ allowed programmers to choose if parts of their code should be strict or lazy.

In 1985, a magazine called BYTE mentioned a program that let you use Hope on early IBM PC DOS computers.