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millfork/docs/lang/literals.md

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[< back to index](../index.md)
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# Literals and initializers
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## Numeric literals
Decimal: `1`, `10`
Binary: `%0101`, `0b101001`
Quaternary: `0q2131`
Octal: `0o172`
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Hexadecimal: `$D323`, `0x2a2`
## String literals
String literals can be used as either array initializers or expressions of type `pointer`.
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String literals are surrounded with double quotes and optionally followed by the name of the encoding:
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"this is a string" ascii
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"this is also a string"
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If there is no encoding name specified, then the `default` encoding is used.
Two encoding names are special and refer to platform-specific encodings:
`default` and `scr`.
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You can also append `z` to the name of the encoding to make the string zero-terminated.
This means that the string will have one extra byte appended, equal to 0.
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"this is a zero-terminated string" asciiz
"this is also a zero-terminated string"z
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Most characters between the quotes are interpreted literally.
To allow characters that cannot be inserted normally,
each encoding may define escape sequences.
Every encoding is guaranteed to support at least
`{n}` for new line,
`{q}` for double quote
and `{apos}` for single quote/apostrophe.
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For the list of all text encodings and escape sequences, see [this page](./text.md).
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In some encodings, multiple characters are mapped to the same byte value,
for compatibility with multiple variants.
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If the characters in the literal cannot be encoded in particular encoding, an error is raised.
However, if the command-line option `-flenient-encoding` is used,
then literals using `default` and `scr` encodings replace unsupported characters with supported ones,
skip unsupported escape sequences, and a warning is issued.
For example, if `-flenient-encoding` is enabled, then a literal `"£¥↑ž©ß{lbrace}"` is equivalent to:
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* `"£Y↑z(C)ss"` if the default encoding is `pet`
* `"£Y↑z©ss"` if the default encoding is `bbc`
* `"?Y^z(C)ss"` if the default encoding is `ascii`
* `"?Y^ž(C)ss"` if the default encoding is `iso_yu`
* `"?Y^z(C)ß"` if the default encoding is `iso_de`
* `"?¥^z(C)ss"` if the default encoding is `jisx`
Note that the final length of the string may vary.
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## Character literals
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Character literals are surrounded by single quotes and optionally followed by the name of the encoding:
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'x' ascii
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'W'
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From the type system point of view, they are constants of type byte.
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For the list of all text encodings and escape sequences, see [this page](./text.md).
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If the characters in the literal cannot be encoded in particular encoding, an error is raised.
However, if the command-line option `-flenient-encoding` is used,
then literals using `default` and `scr` encodings replace unsupported characters with supported ones.
If the replacement is one character long, only a warning is issued, otherwise an error is raised.
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## Array initialisers
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An array is initialized with either:
* a string literal
* a `file` expression
* a `for`-style expression
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* a format, followed by an array initializer:
* `@word` (=`@word_le`): for every term of the array initializer, emit two bytes, first being the low byte of the value, second being the high byte:
`@word [$1122]` is equivalent to `[$22, $11]`
* `@word_be` like the above, but opposite:
`@word_be [$1122]` is equivalent to `[$11, $22]`
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* a list of byte literals and/or other array initializers, surrounded by brackets:
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array a = [1, 2]
array b = "----" scr
array c = ["hello world!" ascii, 13]
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array d = file("d.bin")
array e = file("d.bin", 128, 256)
array f = for x,0,until,8 [x * 3 + 5] // equivalent to [5, 8, 11, 14, 17, 20, 23, 26]
Trailing commas (`[1, 2,]`) are not allowed.
The parameters for `file` are: file path, optional start offset, optional length
(start offset and length have to be either both present or both absent).
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The `for`-style expression has a variable, a starting index, a direction, a final index,
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and a parameterizable array initializer.
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The initializer is repeated for every value of the variable in the given range.