Needed 1+1, built a functional programming language
A programmer recounts the process of building a custom functional programming language in C to solve a data structure problem. The project evolved from a simple expression evaluator into a complex system including closures and garbage collection.
Why it matters
It provides insight into the low-level implementation details of programming language design and compiler construction.
I was given a data structures problem of converting an arithmetic expression into a binary tree. Naturally, I decided to build an evaluator.
A few days later I implemented closures, a garbage collector, a custom memory allocator, a REPL, an FFI, and a whole bunch of other stuff in C.
The problem was: Evaluate 1 + 1 + 1 to 3 using a binary tree.
(+) / \ (+) (1) / \ (1) (1) The operator becomes the root, with its two operands as children.
First, we evaluate the root’s left operand. It’s another + expression, so we have to collapse it down to a value before the outer + can execute.
(3) <--- that's our result We just performed the equivalent of
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