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97 lines
2.8 KiB
Markdown
97 lines
2.8 KiB
Markdown
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[< back to index](../index.md)
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# Preprocessor
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The Millfork preprocessor does 2 things:
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* filters lines in the input file according to current target's features
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* injects the target's feature values as constants into the current file
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Despite its similarity to the C preprocessor, it's much more restricted in its power:
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* no file inclusion
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* no macros
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* separate namespaces for the preprocessor and the language (you need to use `#use` to use a preprocessor constant in the code)
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### Defining feature values
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Feature values are defined in the `[define]` section of the platform definition file.
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Each value is a signed 64-bit integer number.
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Example:
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[define]
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WIDESCREEN=1
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You can also define feature values using the `-D` command line option.
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### Built-in features
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* `ARCH_6502` – 1 if compiling for 6502, 0 otherwise
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* `ARCH_Z80` – 1 if compiling for Z80, 0 otherwise
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### Commonly used features
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* `WIDESCREEN` – 1 if the horizontal screen resolution, ignoring borders, is greater than 256, 0 otherwise
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* `CBM` – 1 if the target is an 8-bit Commodore computer, 0 otherwise
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* `CBM_64` – 1 if the target is an 8-bit Commodore computer compatible with Commodore 64, 0 otherwise
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* `KEYBOARD` – 1 if the target has a keyboard, 0 otherwise
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* `JOYSTICKS` – the maximum number of joysticks using standard hardware configurations, may be 0
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* `HAS_BITMAP_MODE` – 1 if the target has a display mode with every pixel addressable, 0 otherwise
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### Built-in preprocessor functions and operators
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The `defined` function returns 1 if the feature is defined, 0 otherwise.
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All the other functions and operators treat undefined features as if they were defined as 0.
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TODO
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`not`, `lo`, `hi`, `+`, `-`, `*`, `|`, `&`, `^`, `||`, `&&`, `<<`, `>>`,`==`, `!=`, `>`, `>=`, `<`, `<=`
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The following Millfork operators and functions are not available in the preprocessor:
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`+'`, `-'`, `*'`, `<<'`, `>>'`, `:`, `>>>>`, `nonet`, all the assignment operators
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### `#if/#elseif/#else/#endif`
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#if <expr>
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#elseif <expr>
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#else
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#endif
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TODO
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### `#fatal/#error/#warn/#info`
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#error fatal error message
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#error error message
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#warn warning message
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#info informational message
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Emits a diagnostic message.
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`#fatal` interrupts the compilation immediately.
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`#error` causes an error, but the compilation will continue.
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`#warn` emits a warning. It may be treated as an error depending on compilation options.
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`#info` emits a benign diagnostic message.
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### `#use`
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Exports a feature value under its name to the parser.
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The parser will substitute every use of that name as a variable or constant
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with the numeric value of the feature.
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The substitution will happen only within the current file.
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To use such value in other files, consider this:
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#use WIDESCREEN
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const byte is_widescreen = WIDESCREEN
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