Conditionals and Loops

Similar to C++, but a few surprises.

In Rust we’ve got if statement, similar to C or C++, and also if expressions, of the kind found for example in Python.

We’ve also got three keywords for creating loops: for, loop and while.

Github: https://github.com/caveofprogramming/rust/

Logical Operators

These seem to be the same as C++, C and Java. Here is logical and, or and not (with and again) respectively.

This prints:

false

true

true

‘If’ Statements

If statements work similarly to C, C++ or Java, with optional else if and else blocks.

Note, there are no round brackets around the condition. Also, Rust will not consider a zero to be false; you have to put an actual condition in there.

‘If’ Expressions

Rust has an expression form of ‘if’, like Python or Kotlin. In C++ or Java we’d have to use the ternary operator instead.

This is an expression that evaluates to one of two things.

The following code prints “Take jacket”.

Note there are no semi-colons inside the two blocks, and the values in the two blocks must be of the same type.

‘For’ Loops

‘For’ loops are use a range-based syntax, similar to that found in Python or Kotlin. We don’t have the for(;;) syntax that’s found in C.

0..3 ranges over the numbers 0, 1, 2 (exclusive range, excluding the end number) while 0..=3 ranges over 0, 1, 2, 3 (inclusive range, including the end).

I used print!() here to create output all on the same line, and println!() just to create a newline.

If you want to count backwards, you can add on rev(). Then the range needs to be in round brackets.

‘While’ Loops

‘While’ loops work much the same way as in other languages, with the familiar break and continue keywords.

‘Loop’ Loops

There’s also a loop keyword, which creates an infinite loop. To stop it, you have to use the break keyword.

This prints:

1 3 4 5

Labels

You can use labels to break out of an outer loop from within an inner loop. Labels are prefixed with an apostrophe whenever you refer to them.

This prints:

0,0 0,1 0,2 0,3 0,4

1,0 1,1 1,2 1,3 1,4

2,0 2,1 2,2 2,3

Labels don’t seem to work in while loops, at least at the moment, but you can use them with for and loop.