| commit | 2f999111687d352fb36d22db15d00fd929c21543 | [log] [tgz] |
|---|---|---|
| author | Sketch🕴️ <skallywag@sketch.dev> | Sat Feb 28 20:58:17 2026 +0400 |
| committer | Sketch🕴️ <skallywag@sketch.dev> | Sat Feb 28 20:58:17 2026 +0400 |
| tree | 89b7af73753752a1e140dcfef8cefc85dbf5b381 | |
| parent | 547feda05a4f846bb5fa7d32fe10dd10385fd0f0 [diff] |
Step 5: Add Evaluator struct with env, Define, FuncCall support; backward-compat Eval preserved
A math expression evaluator with an interactive REPL, written in Go.
+, -, *, /.5 syntax)* and / bind tighter than + and -)go build -o matheval ./cmd/matheval
Run the REPL:
./matheval
Then type expressions:
>> 2 + 3 * 4 14 >> (2 + 3) * 4 20 >> 7 / 2 3.5 >> 1 / 0 error: division by zero
Press Ctrl+D (EOF) to exit.
You can also pipe input:
echo "2 + 3" | ./matheval
Input string → Lexer → Parser → AST → Evaluator → Result
| Package | Responsibility |
|---|---|
token | Token types and data structures |
lexer | Tokenizes input string |
ast | AST node types (NumberLit, BinaryExpr) |
parser | Recursive-descent parser |
evaluator | Walks AST and computes result |
repl | Read-eval-print loop |
expr → term (('+' | '-') term)*
term → factor (('*' | '/') factor)*
factor → NUMBER | '(' expr ')'
go test ./...
This runs unit tests for each package plus integration tests covering the full pipeline.