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carbon-lang/docs/design/control_flow/conditionals.md
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Chandler CarruthandRichard Smith 94d2c1c6d4 Make proposal filenames use 6 digits and include the title (#7245)
We've talked about adding the title to the filename several times over
the years and it seems really valuable. This requires us to compute a
"slug" for the title spelling that can be part of the filename.

Beyond that, we crossed 7000 recently, and so it seems likely that we
will need to add digits sooner rather than later here, so this goes
ahead and moves us to 6 digits so we don't have to adjust again for a
reasonable length of time.

To implement this and ensure we can sustain it going forward this adds a
tool to our pre-commit that validates (and corrects if needed) the
filename.

In order to update everything and keep links working, there are a _lot_
of changes, but the most interesting for direct review are in
`proposals/scripts`.

Assisted-by: Antigravity with Gemini

---------

Co-authored-by: Richard Smith <richard@metafoo.co.uk>
2026-05-29 00:55:04 +00:00

2.4 KiB

Conditionals

Table of contents

Overview

if and else provide conditional execution of statements. Syntax is:

if (boolean expression ) { statements }

[ else if ( boolean expression ) { statements } ] ...

[ else { statements } ]

Only one group of statements will execute:

  • When the first if's boolean expression evaluates to true, its associated statements will execute.
  • When earlier boolean expressions evaluate to false and an else if's boolean expression evaluates to true, its associated statements will execute.
    • ... else if ... is equivalent to ... else { if ... }, but without visible nesting of braces.
  • When all boolean expressions evaluate to false, the else's associated statements will execute.

When a boolean expression evaluates to true, no later boolean expressions will evaluate.

Note that else if may be repeated.

For example:

if (fruit.IsYellow()) {
  Print("Banana!");
} else if (fruit.IsOrange()) {
  Print("Orange!");
} else if (fruit.IsGreen()) {
  Print("Apple!");
} else {
  Print("Vegetable!");
}
fruit.Eat();

This code will:

  • Evaluate fruit.IsYellow():
    • When True, print Banana! and resume execution at fruit.Eat().
    • When False, evaluate fruit.IsOrange():
      • When True, print Orange! and resume execution at fruit.Eat().
      • When False, evaluate fruit.IsGreen():
        • When True, print Apple! and resume execution at fruit.Eat().
        • When False, print Vegetable! and resume execution at fruit.Eat().

Alternatives considered

References