72 lines
2.1 KiB
Markdown
72 lines
2.1 KiB
Markdown
# The Noja language
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## Introduction
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This language was written as a personal study of how interpreters
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and compilers work. For this reason, the language is very basic.
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One of the main inspirations was the CPython's source code since
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it's extremely readable and has a very simple and clean architecture.
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This file was intended for people who already program in other
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high level languages (such as Python, Javascript, Ruby) and don't
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need to be introduced to basic programming concepts (variables,
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expressions and branches). This way, there is more space for the
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comparison of the language's features with the mainstream languages.
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## Implementation overview
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The interpreter works by compiling the provided source to a bytecode
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format and executing it. The bytecode is very high level since it
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does things like:
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- explicitly referring to variables by name.
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- treating values as atomic things: from the perspective of the
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bytecode, a list and an integer occupy the same space on the
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stack, which is 1.
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- referring to instructions by their index.
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For example, by compiling the following snippet
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```py
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define = true;
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if define:
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a = 33;
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print(a, '\n');
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```
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one would obtain the following bytecode:
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```
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0: PUSHTRU
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1: ASS "define"
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2: POP 1
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3: PUSHVAR "define"
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4: JUMPIFNOTANDPOP 8
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5: PUSHINT 33
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6: ASS "a"
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7: POP 1
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8: PUSHSTR "\n"
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9: PUSHVAR "a"
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10: PUSHVAR "print"
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11: CALL 2
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12: POP 1
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13: RETURN
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```
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as you can see, there are instructions like `ASS` and `PUSHVAR` that
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assign to and read from variables by specifying names, and jumps
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that refer to other points of the "executable" by specifying indices
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(like `JUMPIFNOTANDPOP`) instead of raw addresses.
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All values (objects) are allocated on a garbage-collected heap.
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For this reason all variables are simply references to these objects.
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The garbage collection algorithm is a copy-and-compact one. It
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behaves as a bump-pointer allocator until there is space left,
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and when space runs out, it creates a new heap, copies all of the
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alive object into it, calls the destructors of the dead objects
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and frees the old one. |