Built-in Constants

Constants are used as fallback when a variable is not provided by the user.

Available Constants

Name	Symbol	Value	Description
hbar	ℏ	1.054571817e-34	Reduced Planck (J·s)
e	e	2.71828182845905	Euler's number
pi	π	3.14159265358979	Pi
tau	τ	6.28318530717959	2 * π
phi	φ	1.61803398874989	Golden ratio
gamma	γ	0.57721566490153	Euler-Mascheroni
Omega	Ω	0.56714329040978	Lambda W constant
delta	δ	2.41421356237310	Silver ratio (1+√2)
G	G	6.67430e-11	Gravitational constant
zeta3	ζ(3)	1.20205690315959	Apéry's constant
infty	∞	∞	Infinity
sqrt2	√2	1.41421356237310	Square root of 2
sqrt3	√3	1.73205080756888	Square root of 3
ln2	ln(2)	0.69314718055995	Natural log of 2
ln10	ln(10)	2.30258509299405	Natural log of 10

Usage

Constants can be accessed using their standard LaTeX commands or as variables:

final evaluator = Texpr();

// LaTeX command notation (Recommended for multi-character)
evaluator.evaluateNumeric(r'\hbar');  // 1.05457...
evaluator.evaluateNumeric(r'\pi');     // 3.14159...

// Variable name notation
evaluator.evaluateNumeric('pi');  // 3.14159... (if allowImplicitMultiplication is false)
evaluator.evaluateNumeric('e');   // 2.71828...

TIP

Always use the backslash notation (e.g., \pi, \hbar) for multi-character constants to avoid ambiguity with implicit multiplication of single-letter variables.

Overriding Constants

User-provided variables override built-in constants by default:

// Override 'e' with custom value
e.evaluate('e', {'e': 3.0});  // 3.0

// Constant used when variable not provided
e.evaluate('e');  // 2.71828...

Multi-character Constants

Multi-character constant names (like pi, phi) require using them as variable bindings since the parser only reads single characters:

// Bind pi value to a single-letter variable
e.evaluate(r'\sin{p}', {'p': 3.14159});  // ~0