simple expressions
two flavours
- primitive expressions: eg, 5, +
- applications: eg, (+ 3 4)
what does a scheme interpreter do?
- it evaluates expressions
- eg,
- to save ink, we’ll write instead
evaluating primitive expressions
- the expression 5 just evaluates to the number 5
evaluating applications
- to evaluate (+ 3 4), apply the addition procedure to 3 and 4