fplot

A function plotter built with SDL3 and TinyExpr

Features

• Plot any mathematical expression with variable x
• Real-time rendering with SDL3
• Automatic discontinuity detection
• Grid and axis display
• Support for complex expressions

Prerequisites

Windows

• GCC (MinGW or similar)
• SDL3 library installed at C:\SDL3\ (or update Makefile paths)

Linux

sudo apt-get install libsdl3-dev  # Ubuntu/Debian
sudo dnf install SDL3-devel       # Fedora

macOS

brew install sdl3

Building

Quick Build (Windows)

gcc -Wall -Wextra plot.c tinyexpr.c -IC:\SDL3\include -LC:\SDL3\lib -lSDL3 -lm -o plot.exe

Using Makefile

# Build
make

# Build and run with default function (sin(x))
make run

# Build and run with custom function
make test EXPR="x^2"

# Clean build files
make clean

# Rebuild from scratch
make rebuild

Usage

# Windows
set PATH=C:\SDL3\bin;%PATH%
plot.exe "sin(x)"

# Linux/Mac
./plot "sin(x)"

Example Expressions

./plot "sin(x)"
./plot "x^2"
./plot "cos(x)*exp(-x/5)"
./plot "tan(x)"
./plot "1/x"
./plot "x^3 - 4*x"
./plot "sqrt(abs(x))"
./plot "log(abs(x))"

Supported Functions

TinyExpr supports the following functions:

• Trigonometric: sin, cos, tan, asin, acos, atan, atan2
• Hyperbolic: sinh, cosh, tanh
• Exponential/Logarithmic: exp, log, log10, ln
• Power: pow, sqrt
• Other: abs, ceil, floor, round
• Constants: pi, e

Controls

• Close Window - Click the X button or press Alt+F4

Configuration

Edit the following constants in plot.c to customize:

#define WIDTH 900        // Window width
#define HEIGHT 600       // Window height
#define X_MIN -10.0      // Minimum x value
#define X_MAX 10.0       // Maximum x value
#define Y_MIN -10.0      // Minimum y value
#define Y_MAX 10.0       // Maximum y value
#define STEP 0.01        // Plotting resolution

Project Structure

function-plotter/
├── plot.c          # Main application code
├── tinyexpr.c      # TinyExpr library source
├── tinyexpr.h      # TinyExpr library header
├── Makefile        # Build configuration
└── README.md       # This file

How It Works

1. Expression Parsing: TinyExpr compiles the mathematical expression
2. Coordinate Mapping: Converts mathematical coordinates to screen pixels
3. Plotting: Evaluates the function at small intervals and draws lines
4. Discontinuity Detection: Skips drawing when function has large jumps
5. Rendering: SDL3 renders the grid, axes, and function curve

Limitations

• Plotting range is fixed (-10 to 10 on both axes)
• No zooming or panning
• No multiple function support
• Functions must be continuous or have proper discontinuity handling

Credits

• SDL3 - Simple DirectMedia Layer
• TinyExpr - Mathematical expression parser by Lewis Van Winkle