[asktell]

Every language has its gotchas. Even assignment operators are kind of a gotcha.

If you're coming from a basic math background, and have no programming experience, then the expression "a = 15; a = a + 1;" would be confusing in any mutable language, because assigning a value to a variable is not equivalent to stating the equality (identity) of both sides.

[brlewis]

You're right in that even Scheme, which evolved with teaching in mind, has gotchas. However, the Racket folks made "student languages" that specifically exclude gotchas, so DrRacket is as close as a student can get to a gotcha-free environment.