Change log

This page lists non-trivial changes made to this material during the course. These changes will also be announced on Discord.

Project points will not be taken away due to missing a change that was made to the material during the course.

Thank you to everyone who has pointed out issues!

2024-03-17

• Sandbox: made operators ==, !=, <, <=, > and >= left-associative to match the material, instead of non-associative. You can do either in your project.

2024-03-16

• Project page, Functions: added clarification: ”In this design, you should not consider modules and function definitions themselves to be expressions”.
  • That said, designs where they are expressions are not inherently ”wrong”.
• Project page, renamed unary operator ! -> not to be consistent with other pages. You can use either name.
• Chapter 8: rewrote the dataflow algorithm’s description to be more verbose but precise, especially around initialization and change tracking. The old formulation is here.
• Chapter 8: expanded the section on conservatism a little.

2024-03-15

• Chapter 6, task 2: removed requirement to add == and != to root_types, and explained the reasoning better.

2024-03-12

• assembler.py standard library: fixed read_int bug that could occur if the stack contained non-zero data.

2024-03-11

• assembler.py standard library: print_int fixed to correctly print the smallest possible 64-bit integer: -9223372036854775808.
• Sandbox: fixed incorrect generation of print_int for program var x = 1.
• Chapter 7, task 5: clarified wording.

2024-03-07

• Language spec: mentioned optional semicolons from chapter 3, task 7.

2024-03-01

• Chapter 3, task 7: added a note explaining why inserting a ; after every closing brace is wrong.

2024-02-27

• Sandbox: fixed Assembly generator reserving 8 bytes too much of stack space.
• Chapter 7, task 1: removed a misleading sentence.
• Language spec: added ”You don’t need to support any use of function values other than calling them directly.”
• Sandbox: no longer reserves unnecessary stack space for intrinsics
• Sandbox: fixed stack misalignment on function calls

2024-02-25

• Sandbox: fixed assignment operator not being nestable.

2024-02-21

• Sandbox: fixed type checker not checking that both sides of an assignment operator have the same type.

2024-02-20

• Project page: Functions: added note about possible solutions to functions that exit without executing a return.

2024-02-16

• Sandbox: fixed IR generation bug in short-circuiting where if the right hand side returned an existing variable, it would get overwritten.

2024-02-14

• intrinsics.py: fixed a bug in unary_not: changed 0x1 -> $1. Wthout the $ the number was treated as a memory address.

2024-02-09

• Sandbox: fixed IR generation bug where var x = y didn’t produce a new IR variable.

2024-02-04

• Chapter 8: miscellaneous text improvements and corrections.
• Project page: added ”Dead code elimination (5p)”

2024-02-02

• Language spec, and chapter 3, task 6: clarified that variable declarations are also allowed in top-level expressions.
• Chapter 4: fixed code and picture not matching.
• Sandbox: fixed selection highlighting in browsers other than Firefox.
• Chapter 0: added instructions for running x86-64 Linux code on MacOS. I’ve not had the chance to test this on an ARM Mac yet. Please report issues on Discord.
• Sandbox: required initializer in variable declarations.

2024-02-01

• Sandbox: fixed type checker bug where blocks got the type of their first expression, not the last. Oops.
• Sandbox: fixed incorrect return type of print_int and print_bool.
• Chapter 4, task 4: changed unit testing hint to be simpler and easier.

2024-01-29

• Chapter 7: Improved comments, and cleaned up a couple of unused things in code examples

2024-01-27

• Project page, read-only types: fixed second example

2024-01-26

• Language spec: removed requirement for unit literal.
• Chapter 5, task 3: mentioned assignment operator explicitly, and reordered the list.

2024-01-25

• Language spec: added ”Variable declarations (var ...) are allowed only directly inside blocks ({ ... }).”
• Chapter 3: swapped tasks 5 and 6, and made the above change.

2024-01-24

• Chapter 7: fixed bug in get_all_ir_variables that manifested when a variable is only used in an argument list.
• Chapter 4, tasks 1 & 5: mentioned that the interpreter is allowed to have arbitrary behaviour if the input program would not pass type checking.
• Language spec: added specs for the built-in functions.

2024-01-23

• Course info page: adjusted lecture schedule - Tue 30.1. will be about chapters 6 & 7.

2024-01-22

• Chapter 6 & 7: removed Return IR instruction. You can add it when implementing functions.
• Course info page: adjusted lecture schedule - we’ll probably get through chapters 3-5 tomorrow.

2024-01-21

• Chapter 4: added Any typehints to first interpreter.py example to avoid Python type errors
• Chapter 2, regexes: added paragraph about greedy and non-greedy operators.
• Chapter 2, task 3, bonus task: changed the note to suggest non-greedy repetition instead, as it gives a much easier solution.

2024-01-20

• Chapter 3 and language spec: specified more precedences: unary operators higher than binary operators, and all other constructs higher than all operators.

2024-01-19

• Added the following clarification to the language spec: ”All non-operator expressions such as if, while and function calls must be (syntactically) allowed to be part of other expressions, so e.g. 1 + if true then 2 else 3 must be allowed.”
• Chapter 2, task 3, bonus task: added note that matching multi-line comments may be tricky with vanilla regexes, and explained negative lookahead.

2024-01-18

• Chapter 2, task 1 has been changed to only require tokenizing non-negative integer literals, to avoid an issue pointed out during the lecture.