# Class 15: Scheme Semantics (1)

Back to The Semantics of SIMPLE. On to Scheme Semantics (2).

Held Friday, February 26

Summary

• Assignment 3 distributed.

Contents

Handouts

Notes

• I've updated the syllabus. I've dropped the section on Haskell (which would have been your third functional language) and added a guest-lecture by Dr. Walker for next Wednesday.
• I'll be at a ``master planning'' meeting on technology on campus.
• The Math/CS SEPC is hosting a study break next Monday at 7:30. You are encouraged to attend.

## The Semantics of Scheme

• Notation on p. 40 is important. Make sure you understand it.
• Abstract syntax is fairly straightforward.
• Domain equations begin to get more complex.
• Semantic functions are the interesting ones.

### Terminology

• What are injection and projection?
• They are a lot like type casting.
• One is like casting from a superset/supertype to a subset/suptype (X is declared as an `Object`, but we know that it's really a `Number`, so we call it a number).
• One is like casting from a subset/subtype to a superset/suptype (X is declared as an integer, but I want to treat it as a real).

### Example

• What is the meaning of the equation using ``new'' near the bottom of column 2 of p. 40?

### Typography

• Capital Greek letters are used for ______
• I'll try to use italic uppercase in the web page
• Three-letter combinations are used for ______
• Multi-letter typewriter face is used for ______
• Single-letter typewriter face is used for ______
• Lowercase Greek letters are used for ______
• I'll try to use italic lowercase in the web page
• Italicized Roman words are used for ______
• Capital script letters are used for ______
• I'll try to use bold in the web page

History

• Created Tuesday, January 19, 1999 as a blank outline.
• Filled in the details on Thursday, February 25, 1999. (Taken from the previous outline.)
• Removed some uncovered stuff (and added some covered stuff) on Sunday, February 28, 1999.

Back to The Semantics of SIMPLE. On to Scheme Semantics (2).

Disclaimer Often, these pages were created ``on the fly'' with little, if any, proofreading. Any or all of the information on the pages may be incorrect. Please contact me if you notice errors.