Treecalc

Treecalc is a calculator that shows its work — not just the answer, but exactly how it gets there. Type in an expression like 3 + 4 × (2 − 1), and instead of just spitting out a number, it parses your input into an abstract syntax tree, draws that tree out node by node, and then evaluates it from the bottom up so you can watch operator precedence and parentheses actually do their job. It's built to make parsing and evaluation click. The expression is broken into tokens, assembled into a tree that respects precedence and associativity, and then walked to compute the result — with each stage laid out visually so the usually-invisible machinery of "how does a computer read 2 + 3 × 4" becomes obvious. Step through the evaluation to watch subexpressions collapse into values one at a time, or let it solve instantly if you'd rather see the answer straight away — your choice, remembered as the default. It handles the full set of arithmetic operators, parentheses, negative numbers, and common functions, and it shows you the reverse-Polish (postfix) form too, so the connection between infix, tree, and stack-based evaluation is all in one place. Beyond being a genuinely useful calculator, it's a hands-on way to understand how interpreters and compilers read expressions. A library of curated examples demonstrates specific rules — precedence, associativity, how a unary minus behaves around a power — and a short lesson for each stage of the pipeline comes with its own expression to try, so the idea and the demonstration are never more than a tap apart. Clear error messages point to exactly where an expression breaks, and every calculation you run is kept in a searchable history to revisit later. Everything runs on your device: no account, no connection, no ads. Just an expression, its tree, and the answer built in front of you.