# x65
6502 Macro Assembler in a single c++ file using the struse single file text parsing library. Supports most syntaxes. x65 was recently named Asm6502 but was renamed because Asm6502 is too generic, x65 has no particular meaning.
Every assembler seems to add or change its own quirks to the 6502 syntax. This implementation aims to support all of them at once as long as there is no contradiction.
To keep up with this trend x65 is adding the following features to the mix:
* Full expression evaluation everywhere values are used: [Expressions](#expressions)
* Basic relative sections and linking.
* C style scoping within '{' and '}': [Scopes](#scopes)
* Reassignment of labels. This means there is no error if you declare the same label twice, but on the other hand you can do things like label = label + 2.
* [Local labels](#labels) can be defined in a number of ways, such as leading period (.label) or leading at-sign (@label) or terminating dollar sign (label$).
* [Directives](#directives) support both with and without leading period.
* Labels don't need to end with colon, but they can.
* No indentation required for instructions, meaning that labels can't be mnemonics, macros or directives.
* Conditional assembly with #if/#ifdef/#else etc.
* As far as achievable, support the syntax of other 6502 assemblers (Merlin syntax now requires command line argument).
In summary, if you are familiar with any 6502 assembler syntax you should feel at home with x65. If you're familiar with C programming expressions you should be familiar with '{', '}' scoping and complex expressions.
There are no hard limits on binary size so if the address exceeds $ffff it will just wrap around to $0000. I'm not sure about the best way to handle that or if it really is a problem.
There is a sublime package for coding/building in Sublime Text 3 in the *sublime* subfolder.
## Prerequisite
x65.cpp requires struse.h which is a single file text parsing library that can be retrieved from https://github.com/Sakrac/struse.
### References
* [6502 opcodes](http://www.6502.org/tutorials/6502opcodes.html)
* [6502 opcode grid](http://www.llx.com/~nparker/a2/opcodes.html)
* [Codebase64 CPU section](http://codebase64.org/doku.php?id=base:6502_6510_coding)
## Features
* **Code**
* **Comments**
* **Labels**
* **Directives**
* **Macros**
* **Expressions**
### Code
Code is any valid mnemonic/opcode and addressing mode. At the moment only one opcode per line is assembled.
### Comments
Comments are currently line based and both ';' and '//' are accepted as delimiters.
### <a name="expressions">Expressions
Anywhere a number can be entered it can also be interpreted as a full expression, for example:
```
Get123:
bytes Get1-*, Get2-*, Get3-*
Get1:
lda #1
rts
Get2:
lda #2
rts
Get3:
lda #3
rts
```
Would yield 3 bytes where the address of a label can be calculated by taking the address of the byte plus the value of the byte.
### <a name="labels">Labels
Labels come in two flavors: **Addresses** (PC based) or **Values** (Evaluated from an expression). An address label is simply placed somewhere in code and a value label is follwed by '**=**' and an expression. All labels are rewritable so it is fine to do things like NumInstance = NumInstance+1. Value assignments can be prefixed with '.const' or '.label' but is not required to be prefixed by anything.
*Local labels* exist inbetween *global labels* and gets discarded whenever a new global label is added. The syntax for local labels are one of: prefix with period, at-sign, exclamation mark or suffix with $, as in: **.local** or **!local** or **@local** or **local$**. Both value labels and address labels can be local labels.
```
Function: ; global label
ldx #32
.local_label ; local label
dex
bpl .local_label
rts
Next_Function: ; next global label, the local label above is now erased.
rts
```### <a name="directives">Directives
Directives are assembler commands that control the code generation but that does not generate code by itself. Some assemblers prefix directives with a period (.org
