From 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Sun, 7 Apr 2024 13:41:34 -0500 Subject: new repository --- devdocs/c/language%2Ffor.html | 63 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 devdocs/c/language%2Ffor.html (limited to 'devdocs/c/language%2Ffor.html') diff --git a/devdocs/c/language%2Ffor.html b/devdocs/c/language%2Ffor.html new file mode 100644 index 00000000..010d826f --- /dev/null +++ b/devdocs/c/language%2Ffor.html @@ -0,0 +1,63 @@ +

for loop

Executes a loop.

+

Used as a shorter equivalent of while loop.

+

Syntax

+ +
attr-spec-seq(since C23)(optional) for ( init-clause ; cond-expression ; iteration-expression ) loop-statement

Explanation

Behaves as follows:

+ + +
  • An init-clause, which is a declaration, is in scope in the entire loop body, including the remainder of init-clause, the entire cond-expression, the entire iteration-expression and the entire loop-statement. Only auto and register storage class specifiers are allowed for the variables declared in this declaration.
(since C99)

init-clause, cond-expression, and iteration-expression are all optional. If cond-expression is omitted, it is replaced with a non-zero integer constant, which makes the loop endless:

+
for(;;) {
+   printf("endless loop!");
+}

loop-statement is not optional, but it may be a null statement:

+
for(int n = 0; n < 10; ++n, printf("%d\n", n))
+    ; // null statement

If the execution of the loop needs to be terminated at some point, a break statement can be used anywhere within the loop-statement.

+

The continue statement used anywhere within the loop-statement transfers control to iteration-expression.

+

A program with an endless loop has undefined behavior if the loop has no observable behavior (I/O, volatile accesses, atomic or synchronization operation) in any part of its cond-expression, iteration-expression or loop-statement. This allows the compilers to optimize out all unobservable loops without proving that they terminate. The only exceptions are the loops where cond-expression is omitted or is a constant expression; for(;;) is always an endless loop.

+ + +

As with all other selection and iteration statements, the for statement establishes block scope: any identifier introduced in the init-clause, cond-expression, or iteration-expression goes out of scope after the loop-statement.

+		 (since C99)
+ +

attr-spec-seq is an optional list of attributes, applied to the for statement.

+		 (since C23)

Keywords

for

+

Notes

The expression statement used as loop-statement establishes its own block scope, distinct from the scope of init-clause, unlike in C++:

+
for (int i = 0; ; ) {
+    long i = 1;   // valid C, invalid C++
+    // ...
+}

It is possible to enter the body of a loop using goto. When entering a loop in this manner, init-clause and cond-expression are not executed. (If control then reaches the end of the loop body, repetition may occur including execution of cond-expression.)

+

Example

#include <stdio.h>
+#include <stdlib.h>
+enum { SIZE = 8 };
+int main(void)
+{
+    int array[SIZE];
+    for(size_t i = 0 ; i < SIZE; ++i)
+        array [i] = rand() % 2;
+    printf("Array filled!\n");
+    for (size_t i = 0; i < SIZE; ++i)
+        printf("%d ", array[i]);
+    putchar('\n');
+}

Possible output:

+
Array filled!
+1 0 1 1 1 1 0 0

References

See also

+
C++ documentation for for loop
+

+ © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
+ https://en.cppreference.com/w/c/language/for +

+
-- cgit v1.2.3