derive.c

A symbolic differentiation engine written in C built in a few hours. It parses expressions from text, builds expression trees, computes their derivatives analytically, and simplifies the results. Includes an interactive REPL.

Supported operations

• Arithmetic: addition, subtraction, multiplication, division, negation
• Exponentiation (generalized power rule: d/dx(f^g))
• Trigonometric: sin, cos
• Logarithm: log
• User-defined functions: f = x^2 + 3*x
• Symbolic differentiation: f'(x)
• Evaluation at a point: f(x=5)

Expressions are automatically simplified (e.g. multiplying by 0 or 1, adding 0, constant folding, double negation elimination, canonical ordering of terms).

Building and running

gcc -o derive derive.c -lm -lreadline
./derive

REPL

The program starts an interactive session where you can type expressions, define functions, differentiate, and evaluate:

>> f = x^3 + 2*x
x^3 + 2 * x

>> f'(x)
3 * x^2 + 2

>> f'(x)'(x)
6 * x

>> f(x=4)
72

>> sin(x)^2 + cos(x)^2
sin(x)^2 + cos(x)^2

>> (sin(x)^2 + cos(x)^2)(x=0)
1

>> exit
Goodbye by marcomit!