Jaewoo Kim

Building a Programming Language Before building a compiler, we need to define the language it will compile. A programming language isn’t just syntax and semantics—it’s the user interface between humans and computers. What Is a Programming Language? Abstraction is one of the core ideas in computer science. Without abstraction, interacting with computers would require understanding electrical signals, memory layout, registers, and countless hardware details. A programming language simplifies this complexity. It provides a human-friendly way to express ideas while hiding the low-level mechanisms that make them work. In this sense, a programming language functions as a UI for computing—a layer that lets us focus on building logic, applications, and systems, rather than manually manipulating hardware. ...

Philosophy of SGLang Since the introduction of LLMs, they have been used to solve complex tasks in various fields—including problem-solving, code writing, and answering questions. Today, they are expanding their ability to be agentic, completing tasks users request without human interference. This requires a wide range of prompting techniques, such as skeleton of thought or tree of thought. In other words, we structure LLMs to follow certain patterns to fit our needs, and we require programmability to control and guide them to meet our requirements. ...

Crafting Compilers Compilers This will be a series of posts describing what compilers are, how they are crafted, and how to build your own compiler. Compilers are complicated (sort of) programs that translate high-level programs (written in English mostly) into binary formats that computers can understand. Engineering compilers means designing the way that programs are translated. Let’s first think about what “programs” are, and how they look. I would define a program as a sequence of instructions for hardware to execute. So at the base level, programs are just sets of instructions composed of “1"s and “0"s. One of the original forms of programs was the assembly language used for computers such as the IBM 360. Programmers in the old days wrote hardware instructions directly to make computers run mission-critical programs such as calculating the trajectory of space rockets or managing bank accounts. These directly expressed what the computer should do at each step, and programmers had to be aware of all the hardware details the computer had. They had to manually calculate register usage, memory state, and every hardware detail, or their program would malfunction and blow up their spaceships. ...