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135 lines
4.4 KiB
Markdown
135 lines
4.4 KiB
Markdown
[< back to index](../index.md)
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# Literals and initializers
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## Numeric literals
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Decimal: `1`, `10`
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Binary: `%0101`, `0b101001`
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Quaternary: `0q2131`
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Octal: `0o172`
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Hexadecimal: `$D323`, `0x2a2`
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When using Intel syntax for inline assembly, another hexadecimal syntax is available: `0D323H`, `2a2h`.
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It is not allowed in any other places.
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## String literals
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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.
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Two encoding names are special and refer to platform-specific encodings:
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`default` and `scr`.
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You can also append `z` to the name of the encoding to make the string zero-terminated.
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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
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"this is also a zero-terminated string"z
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Most characters between the quotes are interpreted literally.
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To allow characters that cannot be inserted normally,
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each encoding may define escape sequences.
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Every encoding is guaranteed to support at least
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`{n}` for new line,
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`{q}` for double quote
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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,
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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.
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However, if the command-line option `-flenient-encoding` is used,
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then literals using `default` and `scr` encodings replace unsupported characters with supported ones,
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skip unsupported escape sequences, and a warning is issued.
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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`
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* `"£Y↑z©ss"` if the default encoding is `bbc`
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* `"?Y^z(C)ss"` if the default encoding is `ascii`
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* `"?Y^ž(C)ss"` if the default encoding is `iso_yu`
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* `"?Y^z(C)ß"` if the default encoding is `iso_de`
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* `"?¥^z(C)ss"` if the default encoding is `jisx`
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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.
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However, if the command-line option `-flenient-encoding` is used,
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then literals using `default` and `scr` encodings replace unsupported characters with supported ones.
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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:
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* a string literal
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* a `file` expression
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* a `for`-style expression
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* a format, followed by an array initializer:
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* `@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:
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`@word [$1122]` is equivalent to `[$22, $11]`
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* `@word_be` – like the above, but opposite:
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`@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]
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array b = "----" scr
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array c = ["hello world!" ascii, 13]
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array d = file("d.bin")
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array e = file("d.bin", 128, 256)
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array f = for x,0,until,8 [x * 3 + 5] // equivalent to [5, 8, 11, 14, 17, 20, 23, 26]
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Trailing commas (`[1, 2,]`) are not allowed.
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The parameters for `file` are: file path, optional start offset, optional length
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(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.
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What might be useful is the fact that the compiler allows for built-in trigonometric functions
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in constant expressions only:
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* `sin(x, n)` – returns _n_·**sin**(*x*π/128)
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* `cos(x, n)` – returns _n_·**cos**(*x*π/128)
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* `tan(x, n)` – returns _n_·**tan**(*x*π/128)
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