| ... | ... | @@ -432,18 +432,17 @@ pub fn main() !void { |
| 432 | 432 | </p> |
| 433 | 433 | <p> |
| 434 | 434 | Next, a {#link|public function|Functions#}, {#syntax#}pub fn{#endsyntax#}, named {#syntax#}main{#endsyntax#} |
| 435 | | is declared. The {#syntax#}main{#endsyntax#} function is necessary because it tells the Zig compiler where the start of |
| 436 | | the program exists. Programs designed to be executed will need a {#syntax#}pub fn main{#endsyntax#} function. |
| 435 | is declared. The {#syntax#}main{#endsyntax#} function is necessary because it tells the Zig compiler where the program starts. Programs |
| 436 | designed to be executed will need a {#syntax#}pub fn main{#endsyntax#} function. |
| 437 | 437 | </p> |
| 438 | 438 | <aside role="note" aria-label="Note about main function"> |
| 439 | 439 | <p> |
| 440 | | For more advanced use cases, Zig offers other features to inform the compiler where the start of |
| 441 | | the program exists. Also, libraries do not need a {#syntax#}pub fn main{#endsyntax#} function because |
| 442 | | library code is called by other programs or libraries. |
| 440 | For more advanced use cases, Zig offers other features to inform the compiler where the program starts. Also, libraries do not need a |
| 441 | {#syntax#}pub fn main{#endsyntax#} function because library code is called by other programs or libraries. |
| 443 | 442 | </p> |
| 444 | 443 | </aside> |
| 445 | 444 | <p> |
| 446 | | A function is a block of any number of statements and expressions that, as a whole, perform a task. |
| 445 | A function is a block of any number of statements and expressions, that as a whole, perform a task. |
| 447 | 446 | Functions may or may not return data after they are done performing their task. If a function |
| 448 | 447 | cannot perform its task, it might return an error. Zig makes all of this explicit. |
| 449 | 448 | </p> |
| ... | ... | @@ -469,32 +468,30 @@ pub fn main() !void { |
| 469 | 468 | </aside> |
| 470 | 469 | <p> |
| 471 | 470 | In Zig, a function's block of statements and expressions are surrounded by an open curly-brace <code>{</code> and |
| 472 | | close curly-brace <code>}</code>. Inside of the {#syntax#}main{#endsyntax#} function are expressions that perform |
| 473 | | the task of outputting <samp>Hello, world!</samp> to standard output. |
| 471 | close curly-brace <code>}</code>. In <code class="file">hello.zig</code>, the {#syntax#}main{#endsyntax#} function |
| 472 | contains two statements. |
| 474 | 473 | </p> |
| 475 | 474 | <p> |
| 476 | | First, a constant identifier, {#syntax#}stdout{#endsyntax#}, is initialized to represent standard output's |
| 477 | | writer. Then, the program tries to print the <samp>Hello, world!</samp> |
| 478 | | message to standard output. |
| 475 | In the first statement, a constant identifier, {#syntax#}stdout{#endsyntax#}, is initialized to represent standard output's |
| 476 | writer. In the second statement, the program tries to print the <samp>Hello, world!</samp> message to standard output. |
| 479 | 477 | </p> |
| 480 | 478 | <p> |
| 481 | | Functions sometimes need information to perform their task. In Zig, information is passed |
| 482 | | to functions between an open parenthesis {#syntax#}({#endsyntax#} and a close parenthesis {#syntax#}){#endsyntax#} placed after |
| 483 | | the function's name. This information is also known as arguments. When there are |
| 484 | | multiple arguments passed to a function, they are separated by commas {#syntax#},{#endsyntax#}. |
| 479 | Functions sometimes need inputs to perform their task. Inputs are passed, in between parentheses, to functions. These |
| 480 | inputs are also known as arguments. When multiple arguments are passed to a function, they are separated by commas. |
| 485 | 481 | </p> |
| 486 | 482 | <p> |
| 487 | | The two arguments passed to the {#syntax#}stdout.print(){#endsyntax#} function, {#syntax#}"Hello, {s}!\n"{#endsyntax#} |
| 488 | | and {#syntax#}.{"world"}{#endsyntax#}, are evaluated at {#link|compile-time|comptime#}. The code sample is |
| 489 | | purposely written to show how to perform {#link|string|String Literals and Unicode Code Point Literals#} |
| 490 | | substitution in the {#syntax#}print{#endsyntax#} function. The curly-braces inside of the first argument |
| 491 | | are substituted with the compile-time known value inside of the second argument |
| 492 | | (known as a {#link|tuple|Tuples#}). The <code>\n</code> |
| 493 | | inside of the double-quotes of the first argument is the {#link|escape sequence|Escape Sequences#} for the |
| 494 | | newline character. The {#link|try#} expression evaluates the result of {#syntax#}stdout.print{#endsyntax#}. |
| 495 | | If the result is an error, then the {#syntax#}try{#endsyntax#} expression will return from |
| 496 | | {#syntax#}main{#endsyntax#} with the error. Otherwise, the program will continue. In this case, there are no |
| 497 | | more statements or expressions left to execute in the {#syntax#}main{#endsyntax#} function, so the program exits. |
| 483 | Two arguments are passed to the {#syntax#}stdout.print(){#endsyntax#} function: {#syntax#}"Hello, {s}!\n"{#endsyntax#} |
| 484 | and {#syntax#}.{"world"}{#endsyntax#}. The first argument is called a format string, which is a string containing one or |
| 485 | more placeholders. {#syntax#}"Hello, {s}!\n"{#endsyntax#} contains the placeholder {#syntax#}{s}{#endsyntax#}, which is |
| 486 | replaced with {#syntax#}"world"{#endsyntax#} from the second argument. The file <code class="file">string_literals.zig</code> in |
| 487 | {#link|String Literals and Unicode Code Point Literals|String Literals and Unicode Code Point Literals#} contains examples of format |
| 488 | strings that can be used with the {#syntax#}stdout.print(){#endsyntax#} function. The <code>\n</code> inside of |
| 489 | {#syntax#}"Hello, {s}!\n"{#endsyntax#} is the {#link|escape sequence|Escape Sequences#} for the newline character. |
| 490 | </p> |
| 491 | <p> |
| 492 | The {#link|try#} expression evaluates the result of {#syntax#}stdout.print{#endsyntax#}. If the result is an error, then the |
| 493 | {#syntax#}try{#endsyntax#} expression will return from {#syntax#}main{#endsyntax#} with the error. Otherwise, the program will continue. |
| 494 | In this case, there are no more statements or expressions left to execute in the {#syntax#}main{#endsyntax#} function, so the program exits. |
| 498 | 495 | </p> |
| 499 | 496 | <p> |
| 500 | 497 | In Zig, the standard output writer's {#syntax#}print{#endsyntax#} function is allowed to fail because |