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Below is a snippet of the C standard(section 6.8.5 of the n1256 TC3 C99).
iteration-statement:
while ( expression ) statement
do statement while ( expression ) ;
for ( expressionopt ; expressionopt ; expressionopt ) statement
for ( declaration expressionopt ; expressionopt ) statement
What piques my interest is the last statement: for ( declaration expression ; expression ) statement. 6.8.5.1 explains the for loop, but only mentions the for ( clause-1 ; expression-2 ; expression-3 ) statement syntax.
I did a few attempts at writing code according to this syntax, but they all gave me syntax errors. Examples:
for (int i = 0, i; i++) { /* ... */ } for (int i = 0; !(i++)) { /* ... */ } Which all results in errors similar to error: expected ‘;’ before ‘)’ token when compiled using GCC(v4.9.2).
I'm not sure if I'm interpreting the standard in the right way. Can this syntax be used in some useful way, or have I overlooked something?
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Array. filter, map, some have the same performance as forEach. These are all marginally slower than for/while loop. Unless you are working on performance-critical functionalities, it should be fine using the above methods.
Java provides three repetition statements/looping statements that enable programmers to control the flow of execution by repetitively performing a set of statements as long as the continuation condition remains true. These three looping statements are called for, while, and do… while statements.
Use a for loop when you know the loop should execute n times. Use a while loop for reading a file into a variable. Use a while loop when asking for user input. Use a while loop when the increment value is nonstandard.
Unfortunately, this is not easy to read. You are misreading the second case of the for statement. The first semicolon is an integral part of declaration and thus hidden to your eyes. You can easily check such syntax questions by looking into Annex A. There you have:
(6.7) declaration: declaration-specifiers init-declarator-listopt ; static_assert-declaration If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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