81 lines
4.0 KiB
HTML
81 lines
4.0 KiB
HTML
---
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layout: soml
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title: Salama object machine language
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---
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<div class="row">
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<div class="span10">
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<h4>Top down designed language</h4>
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<p>
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Soml is a language that is designed to be compiled into, rather than written, like
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other languages. It is the base for a higher system,
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designed for the needs to compile ruby. It is not an endeavour to abstract from a
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lower level, like other system languages, namely off course c.<br/>
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Still it is a system language, or an object machine language, so almost as low level a
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language as possible. Only assembler is really lower, and it could be argued that assembler
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is not really a language, rather a data format for expressing binary code. <br/>
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</p>
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</div>
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</div>
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<div class="row">
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<div class="span10">
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<h5>Object oriented to the core, including calling convention</h5>
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<p>
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Soml is completely object oriented and strongly typed. For types, the classes are used, but
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the main distinction is between object (references) and integers. This is off course
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essential as dereferencing integers is what we want to avoid.
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</p>
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<p>
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The object model, ie the basic properties of objects that the system relies on, is quite simple
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and explained below. It involves a single reference per object. <br/> Also the object memory
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model is kept quite simple in that objects are always small multiples of the cache size of the
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hardware machine. We use object encapsulation to build up larger looking objects from these
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basic blocks.
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</p>
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<p>
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The calling convention is also object oriented, not stack based*. Message objects used to
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define the data needed for invocation. They carry arguments, a frame and return addresses.
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In Soml return addresses are pre-calculated and determined by the caller, and yes, there
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are several. In fact there is one return address per masic type, plus one for exception.
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A method invocation may thus be made to return to an entirely different location than the
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caller.
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*(A stack, as used in c, is not typed and as such a source of problems)
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</p>
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<p>
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There is no non- object based memory in soml. The only global constants are instances of
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classes that can be accessed by writing the class name in soml source.
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</p>
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</div>
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</div>
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<div class="row">
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<div class="span10">
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<h5>Syntax and runtime</h5>
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<p>
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Soml syntax is a mix between ruby and c. I is like ruby in the sense that semicolons and even
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newlines are not neccessary unless they are. It still uses braces, but that will probably
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be changed. <br/>
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But off course it is typed, so in argument or variable definitions the type must be specified
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like in c. Types are classes, but int may be used for brevity instead of Integer. Return
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types are also declared, though more for statci analysis. As mentioned any function may return
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to differernt addresses according to type. The compiler automatically inserts erros for
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return typesa that are not handled by the caller. <br/>
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The complete syntax and their translation is discussed <a href="syntax.html"> here </a>
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</p>
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<p>
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As soml is the base for dynamic languages, all compile information is recorded in the runtime.
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All inforamtion is off course object oriented, ie in the form off objects. This means a class
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hierachy and this itself is off course part of the runtime. The runtime, Parfait, is kept
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to a minnimum, currently around 15 classes, described in detail <a href="parfait.html">
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here </a>. <br/>
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Historically Parfait has been coded in ruby, as it was first needed in the compiler.
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This had the additional benefit of providing solid test cases for the functionality.
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Currently the process is to recode the same functionality in soml, and by the end of that
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a converter will be written. This will convert the soml code into ruby code, thus removing the
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duplication.
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</p>
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</div>
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</div>
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