Apple-2-SW/prog8
1
0
Fork 0
mirror of https://github.com/irmen/prog8.git synced 2025-02-22 01:29:07 +00:00
Code Issues Projects Releases Wiki Activity

emphasize that str[] is also split by default

Browse Source
This commit is contained in:
Irmen de Jong 2024-12-27 17:00:39 +01:00
parent bdccffbb8e
commit b6e1fb3ba8
1 changed files with 7 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
docs/source/variables.rst
View File

@ -168,7 +168,7 @@ type identifier type storage size example var declara
``uword[]`` unsigned word array depends on value ``uword[] myvar = [1, 2, 3, 4]``
``float[]`` floating-point array depends on value ``float[] myvar = [1.1, 2.2, 3.3, 4.4]``
``bool[]`` boolean array depends on value ``bool[] myvar = [true, false, true]`` note: consider using bit flags in a byte or word instead to save space
``str[]`` array with string ptrs 2*x bytes + strs ``str[] names = ["ally", "pete"]``
``str[]`` array with string ptrs 2*x bytes + strs ``str[] names = ["ally", "pete"]`` note: equivalent to a uword array.
``str`` string (PETSCII) varies ``str myvar = "hello."``
implicitly terminated by a 0-byte
=============== ======================= ================= =========================================
@ -326,11 +326,14 @@ Unlike array variables, negative indexing for pointer variables does *not* mean
Instead, it simply addresses memory that lies *before* the pointer variable.
See also :ref:`pointervars`
**LSB/MSB split word arrays:**
**LSB/MSB split word and str arrays:**
As an optimization, (u)word arrays are split by the compiler in memory as two separate arrays,
As an optimization, (u)word arrays and str arrays are split by the compiler in memory as two separate arrays,
one with the LSBs and one with the MSBs of the word values. This is more efficient to access by the 6502 cpu.
It also enables a maximum length of 256 for word arrays, where normally it would have been 128.
It also allows a maximum length of 256 for word arrays, where normally it would have been 128.
For normal prog8 array indexing, the compiler takes care of the distiction for you under water.
*But for assembly code, or code that otherwise accesses the array elements directly, you have to be aware of the distinction from 'normal' arrays.*
In the assembly code, the array is generated as two byte arrays namely ``name_lsb`` and ``name_msb``, immediately following eachother in memory.
The ``@split`` tag can be added to the variable declaration to *always* split the array even when the command line option -dontsplitarrays is set