MathJSON

MathJSON is compute-engine's expression AST — the most explicit input form, and what every other input (LaTeX, …) parses into. A notatio component takes it via format="mathjson".

The shape

An expression is a number, a string (a symbol), or a function as an array ["Head", ...args]:

Toggle the Out form (hover the label) to FullForm to read the MathJSON back, or StandardForm/TeXForm to see it typeset.

Atoms

• Numbers are JSON numbers: 2, -3.5, 1.5e3. For exact values beyond a double, use a string-wrapped number { "num": "123456789012345678" }.
• Symbols are strings: "x", "Pi", "ExponentialE". Reserved constants have canonical names — Pi, ExponentialE (e), ImaginaryUnit (i), PositiveInfinity.
• Strings (text, not symbols) are wrapped: ["String", "hello"].

Footguns

• A symbol is a string, a string literal is wrapped. "Pi" is the constant π; a literal word is ["String", "Pi"]. Bare "2" is not the number 2 — numbers are JSON numbers, so write 2.
• Rationals stay exact. ["Rational", 1, 2] is ½, not 0.5. Writing 0.5 gives a float. This matters downstream: the NumPy target has no rationals and collapses ["Rational",1,2] to 0.5.
• Function heads are capitalised. It's ["Sin", "x"], not ["sin","x"].
• Lists are a head too. ["List", 1, 2, 3], not a bare JSON array at the top level — the outermost array is always [head, ...args].