024aa9a345
The book was located under 'src/doc/trpl' because originally, it was going to be hosted under that URL. Late in the game, before 1.0, we decided that /book was a better one, so we changed the output, but not the input. This causes confusion for no good reason. So we'll change the source directory to look like the output directory, like for every other thing in src/doc.
80 lines
2.3 KiB
Markdown
80 lines
2.3 KiB
Markdown
% Glossary
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Not every Rustacean has a background in systems programming, nor in computer
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science, so we've added explanations of terms that might be unfamiliar.
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### Abstract Syntax Tree
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When a compiler is compiling your program, it does a number of different things.
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One of the things that it does is turn the text of your program into an
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‘abstract syntax tree’, or ‘AST’. This tree is a representation of the structure
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of your program. For example, `2 + 3` can be turned into a tree:
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```text
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+
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/ \
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2 3
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```
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And `2 + (3 * 4)` would look like this:
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```text
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+
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/ \
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2 *
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/ \
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3 4
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```
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### Arity
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Arity refers to the number of arguments a function or operation takes.
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```rust
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let x = (2, 3);
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let y = (4, 6);
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let z = (8, 2, 6);
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```
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In the example above `x` and `y` have arity 2. `z` has arity 3.
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### Bounds
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Bounds are constraints on a type or [trait][traits]. For example, if a bound
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is placed on the argument a function takes, types passed to that function
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must abide by that constraint.
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[traits]: traits.html
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### DST (Dynamically Sized Type)
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A type without a statically known size or alignment. ([more info][link])
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[link]: ../nomicon/exotic-sizes.html#dynamically-sized-types-dsts
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### Expression
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In computer programming, an expression is a combination of values, constants,
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variables, operators and functions that evaluate to a single value. For example,
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`2 + (3 * 4)` is an expression that returns the value 14. It is worth noting
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that expressions can have side-effects. For example, a function included in an
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expression might perform actions other than simply returning a value.
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### Expression-Oriented Language
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In early programming languages, [expressions][expression] and
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[statements][statement] were two separate syntactic categories: expressions had
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a value and statements did things. However, later languages blurred this
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distinction, allowing expressions to do things and statements to have a value.
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In an expression-oriented language, (nearly) every statement is an expression
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and therefore returns a value. Consequently, these expression statements can
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themselves form part of larger expressions.
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[expression]: glossary.html#expression
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[statement]: glossary.html#statement
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### Statement
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In computer programming, a statement is the smallest standalone element of a
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programming language that commands a computer to perform an action.
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