cfcompiler's Introduction

Compiler for the CF language by Kevin Hammond

#Design Decisions

I decided to interpret while (condition) don't {dostuff} as while (not condition) do {dostuff}.
I decided to implement the comefrom statement by making each label a goto statement and each comefrom a label. This requires that every label has exactly one comefrom statement and vice versa. The alternative is to perform an additional pass over the AST to determine which labels are unneccessary.

#Features

I have introduced an extra AST node type - the Line class - to represent a line of code. If a node within the line fails to compile, the error message can include the line number and context.
If a stat fails to compile within a Stats node, the compiler will log the failure and attempt to continue compiling. This allows it to detect multiple compilation failures while compiling. lines
One problem with the comefrom statement is that the stack may be different at the label to what is at the comefrom. To stop this, I decided that label-comefrom pairs must be within the same stats list, where the stack will always be the same.
Comefrom statements may also allow a variable declaration to be skipped (e.g. l;new x=5;comefrom l;print x would cause problems). The Stats compiler class checks for this possibility and logs an error if it happens.

Future Work

Tiling - boolean operations (among others) such as the not operation would benefit from a tiling algorithm to remove useless code.
More control flow in the language, such as if statements.
Integration of a lexer.

#Build Instructions