Futurebasic/Language/Reference/compile long if
COMPILE LONG IF statement
[edit | edit source]COMPILE LONG IF
[edit | edit source]Statement
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Syntax
[edit | edit source]COMPILE LONG IF condition
[statementBlock1]
[COMPILE XELSE
[statementBlock2]]
COMPILE END IF
Description
[edit | edit source]You can use the COMPILE LONG IF statement to conditionally include or exclude selected lines of code from the compiled version of your program. This is useful if you need to maintain two (or more) slightly different versions of your program; COMPILE LONG IF allows you to maintain them both within the same source file.
If the condition following COMPILE LONG IF is evaluated as "true" or non-zero, then the statements in statementBlock1 are included in the compilation and the statements (if any) in statementBlock2 are ignored by the compiler. If the condition is evaluated as "false" or zero, then the statements in statementBlock1 are ignored by the compiler, and the statements (if any) in statementBlock2 are included in the compilation.
condition must be in one of the following forms:
constExpr{DEF | NDEF} _symbolicConstantTRON [= _false]cpu68KcpuPPCcarbonLib- A list of any of the above separated by "
AND" or "OR". You may also optionally surround any valid sub-condition with parentheses.
constExpr is a "static integer expression." A static integer expression is any valid expression which consists of only:
- integer literal constants;
- previously-defined symbolic constant names;
- operators (like +, -, *, /, >, =);
- parentheses
(In particular, it can't contain variables, nor function references.) If you use this form of COMPILE LONG IF, then the condition will be evaluated as "true" if the expression's value is nonzero.
_symbolicConstant stands for a symbolic constant name. DEF_symbolicConstant is evaluated as "true" if the indicated constant was previously defined. NDEF_symbolicConstant is evaluated as "true" if the indicated constant was not previously defined.
The condition TRON is evaluated as "true" if debugging has been activated for the current section of code. The condition TRON = _false is evaluated as "true" if debugging has not been activated for the current section of code. (See the <a href="tron.html">TRON</a> statement for more details.)
If you use the keyword cpu68K as the condition, it's evaluated as "true" if the current compilation is being compiled into Motorola 680x0 ("68k") machine code. If you use the keyword cpuPPC as the condition, it's evaluated as "true" if the current compilation is being compiled into PowerPC machine code.
Example
[edit | edit source]Because COMPILE LONG IF can cause lines (including non-executable lines) to be completely ignored by the compiler, you can use it to control such things as the declaration of variables, program labels, constants, and even entire functions. For example:
COMPILE LONG IF _needBigArray
DIM myArray&(3000)
COMPILE XELSE
DIM myArray&(30)
COMPILE END IF
COMPILE LONG IF _dimensions = 3
DEF FN Diagonal!(a!, b!, c!) = SQR(a!*a! + b!*b! + c!*c!)
COMPILE XELSE
DEF FN Diagonal!(a!, b!) = SQR(a!*a! + b!*b!)
COMPILE END IF
Note:
COMPILE LONG IF blocks can be nested to a depth of 16 levels.