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Preprocessor ifdef else

The if directive, with the elifelseand endif directives, controls compilation of portions of a source file. If the expression you write after the if has a nonzero value, the line group immediately following the if directive is kept in the translation unit. Each if directive in a source file must be matched by a closing endif directive. Any number of elif directives can appear between the if and endif directives, but at most one else directive is allowed.

The else directive, if present, must be the last directive before endif. The ifelifelseand endif directives can nest in the text portions of other if directives. Each nested elseelifor endif directive belongs to the closest preceding if directive. All conditional-compilation directives, such as if and ifdefmust match a closing endif directive before the end of file.

Otherwise, an error message is generated. When conditional-compilation directives are contained in include files, they must satisfy the same conditions: There must be no unmatched conditional-compilation directives at the end of the include file. Macro replacement is done within the part of the line that follows an elif command, so a macro call can be used in the constant-expression. The preprocessor selects one of the given occurrences of text for further processing.

A block specified in text can be any sequence of text. Il peut occuper plusieurs lignes. It can occupy more than one line. Usually text is program text that has meaning to the compiler or the preprocessor.

The preprocessor processes the selected text and passes it to the compiler. If text contains preprocessor directives, the preprocessor carries out those directives.

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Only text blocks selected by the preprocessor are compiled. The preprocessor selects a single text item by evaluating the constant expression following each if or elif directive until it finds a true nonzero constant expression.

It selects all text including other preprocessor directives beginning with up to its associated elifelseor endif. If all occurrences of constant-expression are false, or if no elif directives appear, the preprocessor selects the text block after the else clause. When there's no else clause, and all instances of constant-expression in the if block are false, no text block is selected. Expressions must have integral type and can include only integer constants, character constants, and the defined operator.

The expression can't use sizeof or a type-cast operator. The target environment may be unable to represent all ranges of integers.

The translation represents type int the same way as type longand unsigned int the same way as unsigned long. The translator can translate character constants to a set of code values different from the set for the target environment. Macros H.

preprocessor ifdef else

To determine the properties of the target environment, use an app built for that environment to check the values of the LIMITS. H macros. The expression must not query the environment, and must remain insulated from implementation details on the target computer. This constant expression is considered true nonzero if the identifier is currently defined. Otherwise, the condition is false 0. An identifier defined as empty text is considered defined. The defined operator can be used in an if and an elif directive, but nowhere else.

If neither identifier is defined, the call to printerror is compiled. The conditional compilation statements in the following example assume a previously defined symbolic constant named DLEVEL. The first if block shows two sets of nested ifelseand endif directives. Otherwise, the statements after else are processed.The preprocessor include the instructions for the compiler, these instructions are executed before the source code is compiled. Preprocessor directives begin with hash sign.

No semicolon ; is expected at the end of a preprocessor directive. The define preprocessor directive define the macro-name and value, this value is replaced with each time the macro-name appears in the program. The define preprocessor directive can be used as inline function which is replaced at compile time.

The definition of macro accepts an argument and that argument is replaced by the actual argument found in program. The include preprocessor directive is used to include another source file in our source code. This is commonly used to include header files in our program. The source file to be added must be enclosed within double quotes " " or angle brackets. If the file is enclosed in double quotes the search will be done in current directory.

If the file is enclosed in angle brackets the search will be done in standard directories include directory where the libraries are stored.

Conditional Compilation In C: #ifdef #else #endif

The if preprocessor directive takes condition in parenthesis, if condition is true, then the statements given between if and else will get execute. If condition is false, then statements given between else and endif will get execute.

The elif preprocessor directive is similar to if-else ladder statement. It is used for checking multiple conditions, if the first condition will not satisfy, compiler will jump to else block and check other condition is true or not and so on.

#if, #elif, #else, and #endif directives (C/C++)

The ifdef preprocessor directive is used to check whether the macro-name is previously defined or not, if defined then the statements given between ifdef and else will get execute.

The ifndef preprocessor directive is used to check whether the macro-name is previously defined or not, if not defined then the statements given between ifndef and else will get execute. The above code is still in LineDemo.

The error preprocessor directive is used to force the compile to stop compiling the source code. In other words we can manually force the compiler to stop compiling and give fatal error.

The only difference between example 1 and 2 is the statement 1.The if directive, with the elifelseand endif directives, controls compilation of portions of a source file. If the expression you write after the if has a nonzero value, the line group immediately following the if directive is kept in the translation unit. Each if directive in a source file must be matched by a closing endif directive. Any number of elif directives can appear between the if and endif directives, but at most one else directive is allowed.

The else directive, if present, must be the last directive before endif. The ifelifelseand endif directives can nest in the text portions of other if directives.

Each nested elseelifor endif directive belongs to the closest preceding if directive. All conditional-compilation directives, such as if and ifdefmust match a closing endif directive before the end of file. Otherwise, an error message is generated. When conditional-compilation directives are contained in include files, they must satisfy the same conditions: There must be no unmatched conditional-compilation directives at the end of the include file.

Macro replacement is done within the part of the line that follows an elif command, so a macro call can be used in the constant-expression. The preprocessor selects one of the given occurrences of text for further processing.

preprocessor ifdef else

A block specified in text can be any sequence of text. It can occupy more than one line. Usually text is program text that has meaning to the compiler or the preprocessor. The preprocessor processes the selected text and passes it to the compiler. If text contains preprocessor directives, the preprocessor carries out those directives. Only text blocks selected by the preprocessor are compiled.

Preprocessor directives

The preprocessor selects a single text item by evaluating the constant expression following each if or elif directive until it finds a true nonzero constant expression. It selects all text including other preprocessor directives beginning with up to its associated elifelseor endif. If all occurrences of constant-expression are false, or if no elif directives appear, the preprocessor selects the text block after the else clause.

When there's no else clause, and all instances of constant-expression in the if block are false, no text block is selected.

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The constant-expression is an integer constant expression with these additional restrictions:. Expressions must have integral type and can include only integer constants, character constants, and the defined operator. The translation represents type int the same way as type longand unsigned int the same way as unsigned long.

The translator can translate character constants to a set of code values different from the set for the target environment. To determine the properties of the target environment, use an app built for that environment to check the values of the LIMITS. H macros. The expression must not query the environment, and must remain insulated from implementation details on the target computer. The preprocessor operator defined can be used in special constant expressions, as shown by the following syntax:.

This constant expression is considered true nonzero if the identifier is currently defined. Otherwise, the condition is false 0. An identifier defined as empty text is considered defined. The defined operator can be used in an if and an elif directive, but nowhere else. In the following example, the if and endif directives control compilation of one of three function calls:.

If neither identifier is defined, the call to printerror is compiled. The conditional compilation statements in the following example assume a previously defined symbolic constant named DLEVEL.

The first if block shows two sets of nested ifelseand endif directives. Otherwise, the statements after else are processed.Preprocessor conditional compilation directives allow compiling or skipping a part of the program depending on the fulfillment of a certain condition.

Any of the conditional compilation directives can be followed by any number of lines possibly containing else directive and ending with endif. If the verified condition is true, the lines between else and endif are ignored. If the verified condition is not fulfilled, all lines between checking and else directive or endif directive if the former is absent are ignored.

Depending on the program type and compilation mode, the standard macros are defined the following way:. MQL4 Reference Language Basics Preprocessor Conditional Compilation ifdef, ifndef, else, endif Macro substitution define Program Properties property Including Files include Importing Functions import Conditional Compilation ifdef, ifndef, else, endif Conditional Compilation ifdef, ifndef, else, endif Preprocessor conditional compilation directives allow compiling or skipping a part of the program depending on the fulfillment of a certain condition.

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That condition can take one of the following forms. Importing Functions import Object-Oriented Programming.

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Macro substitution define Program Properties property Including Files include Importing Functions import Conditional Compilation ifdef, ifndef, else, endif. Conditional Compilation ifdef, ifndef, else, endif Preprocessor conditional compilation directives allow compiling or skipping a part of the program depending on the fulfillment of a certain condition.Preprocessor directives Preprocessor directives are lines included in the code of programs preceded by a hash sign.

These lines are not program statements but directives for the preprocessor. The preprocessor examines the code before actual compilation of code begins and resolves all these directives before any code is actually generated by regular statements. These preprocessor directives extend only across a single line of code. As soon as a newline character is found, the preprocessor directive is ends. No semicolon ; is expected at the end of a preprocessor directive. Its syntax is: define identifier replacement When the preprocessor encounters this directive, it replaces any occurrence of identifier in the rest of the code by replacement.

This replacement can be an expression, a statement, a block or simply anything. Its compilation began Nov 1 at A string literal in the form "Mmm dd yyyy" containing the date in which the compilation process began. A string literal in the form "hh:mm:ss" containing the time at which the compilation process began. An integer value.

Note that many compilers are not fully conforming and thus will have this constant defined as neither of the values above. In C: if defined to 1the implementation conforms to the C standard. Previous: Exceptions.Join Stack Overflow to learn, share knowledge, and build your career. Connect and share knowledge within a single location that is structured and easy to search. But substituting elif causes it to work as expected based on what's defined. What convoluted purpose, if any, is served by the existence of elseif?

And if none, why doesn't the preprocessor complain? The preprocessor doesn't complain because your ifdef is false, and the directives within that ifdef block are not parsed. To illustrate it, this code is valid:. Learn more. Asked 4 years, 11 months ago. Active 2 years, 1 month ago. Viewed 8k times. I have found that writing ifdef Improve this question. Jerry Miller Jerry Miller 7 7 silver badges 11 11 bronze badges. If the thing after ifdef is defined, you should see an "Invalid preprocessing directive" error.

Only elif exists: en. Add a comment. Active Oldest Votes. Improve this answer. Yexo Yexo 1, 14 14 silver badges 21 21 bronze badges. Pete Klammer Pete Klammer 1. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

preprocessor ifdef else

Post as a guest Name. Email Required, but never shown. The Overflow Blog. Best practices can slow your application down. Featured on Meta.Follow Easyodds to get the best value when you win.

Easyodds uses cookies to give you the best possible experience. Full cookie policy details here. OK Well what do you think. Email: Comment: Be the first to know. You can use our odds comparison matrices, to add a selection to your basket. College football betting odds: SEC Week 12 games (offshore odds) Spenser Davis Posted 4 weeks ago With 11 weeks of college football in the books, will Week 12 be the time to get aggressive with your money.

The Rebels are three-point favorites over the Aggies in a matchup of teams that could be entering the head coach market at the same time this offseason.

The Crimson Tide will host Mercer (no line) while Auburn opens as a 35. The second closest game of the week is expected to be Missouri at Vanderbilt.

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Georgia is a 22-point favorite over Kentucky after getting crushed by Auburn over the weekend. Kentucky is coming off a win and is looking for its first 8-win season since 2007. Next up are two teams that fired their coach midseason, Florida and Tennessee.

The Gators are 11 point favorites over UAB while Tennessee, in its first game without Butch Jones, will be a 14.

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So, make your picks and get ready to make your moves over at MyBookie. Note: These lines were taken from VegasInsider.

C++ preprocessor #if #else #endif #include

All games are Saturday. Conor McGregor fight is drawing so much interest. Betting odds for Conor McGregor continue to improve thanks to sizable wagers rolling in on the Irishman for his fight against Floyd Mayweather.

Editor's Picks'The Super Bowl of boxing': How Vegas made Mayweather-McGregor oddsThe last time famous Las Vegas oddsmaker Jimmy Vaccaro made a fighter a -2,700 favorite, the year was 1990 and Mike Tyson was fighting Buster Douglas. Here is the story of how Vegas made odds on the Floyd Mayweather-Conor McGregor fight. Here is a running file of the biggest Mayweather-McGregor bets across Nevada sportsbooks.

Across town at the South Point sportsbook on Monday afternoon, another big wager came in on a McGregor prop bet with a better payout. The Mayweather-McGregor fight will take place on Saturday, Aug. The Week 10 slate starts with a bang thanks to a divisional game in the Thursday slot and doesn't let up. Like the week prior, it boasts more unfamiliar teams against one another in interconference showdowns, such as when the New Orleans Saints collide with the Buffalo Bills.

Thanks to these unusual matchups, the lines set by oddsmakers out of Las Vegas can seem akin to a minefield for those bettors looking to build a bankroll over the second half of the season. Below, let's get an early glance at the full set of lines and nail down some predictions. NFL Week 10 Schedule, OddsLuckily for bettors, the divisional game to start the stretch looks timid.

On paper, the Seattle Seahawks shouldn't have many problems with the Arizona Cardinals. Russell Wilson's team has looked good on the road this year at 2-2 (the losses coming against Aaron Rodgers and Marcus Mariota, which are acceptable), squashing that particular narrative.

This has to do with the Cardinals more than anything, though. The team has four wins on the season, but said marks in the victory column have come against:Those are not great wins, and here's the kickeronly one of those games had a final by more than a touchdown margin and two needed overtime.

These Cardinals aren't doing anything particularly well and are down one of the league's best running backs in David Johnson, not to mention starting quarterback Carson Palmer.

The Seahawks have won four of five, the only loss over the span being a three-point affair. Wilson keeps excelling behind a poor offensive line and is up to 17 touchdowns and six interceptions, while his defense boasts 23 sacks and eight interceptions while only permitting 18.

This would be a scarier line if the Cardinals were healthy, but they instead boast an inflated record and help create a matchup ripe for bettors to take advantage of while starting the week off right.

It's an odd season when bettors can count on a three-win Chicago Bears team for a good payout.


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