Eval

Simple numerical expression evaluator

Features

• Single source file, single header (excluding example main.c file)
• MIT license - Permits use in open and closed source projects
• Written in ANSI C - Eval should run on more or less any platform
• No external dependencies beyond standard libraries (string.h math.h)
• Single argument functions
• Variable substitution

Why?

Because I needed a small expression evaluator for use in a Cortex-M4 based firmware project I was working on.

Syntax

Terms

123, 4e5, 3.2, 7.4e-5       Numeric literal.
$name                       Variable names may contain A-Z, a-z, 0-9 and _ character (but cannot start with 0-9).
func(arg)                   Function names follow the same convenion as variables names.

Unary Operators

-                           Negates operand.

Binary Operators

+                           Adds right operand to left operand.
-                           Subtracts right operand from left operand.
*                           Multplies left operand by right operand.
/                           Divides left operand by right operand.

Default Variables

$INFINITY                   Infinity.
$NAN                        IEEE754 'not a number' special value.
$PI                         3.14159265358979

Default Functions

These functions are aliases of those found in math.h:

cos
sin
tan
acos
asin
atan
exp
log
log10
log2
sqrt
cbrt
ceil
floor
round